SELECT IC.InsCarrierId,IC.InsCarrierName,
ID.InterchangeControlId,ID.InterchangeName
FROM InsCarrier IC
LEFT OUTER JOIN InterchangeControl ID ON ID.InterchangeControlId=IC.InterchangeControlId
WHERE IC.InsCarrierName LIKE '%'+ @InsCarrierName + '%' --AND ID.InterchangeControlId=@InterchangeControlId
Monday 29 November 2010
Saturday 20 November 2010
Textbox Control Events in C#
basic events that are very helpful while developing an Application.
To begin with this application create a windows form and drop two textbox control and listbox control. Define the following events for the textbox controls:
Enter Event.
GotFocus Event.
KeyDown Event.
KeyUp Event.
KeyPress Event.
Leave Event.
LostFocus Event.
To check when which occurs I hav used listbox control in which the message is displayed when the respective event will occur. Code for these Events is as follows:
Events for the Textbox control1:
void textBox1_LostFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("LostFocus event called of TextBox1");
}
void textBox1_GotFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("GotFocus event called of TextBox1");
}
void textBox1_Leave(object sender, System.EventArgs e)
{
listBox1.Items.Add("Leave event called of TextBox1");
}
void textBox1_KeyUp(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyUp event called of TextBox1");
}
void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
listBox1.Items.Add("KeyPress event called of TextBox1");
}
void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyDown event called of TextBox1");
}
void textBox1_Enter(object sender, System.EventArgs e)
{
listBox1.Items.Add("Enter event called of TextBox1");
}
Events for the Textbox control2:
void textBox2_LostFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("LostFocus event called of TextBox2");
}
void textBox2_GotFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("GotFocus event called of TextBox2");
}
void textBox2_Leave(object sender, System.EventArgs e)
{
listBox1.Items.Add("Leave event called of TextBox2");
}
void textBox2_KeyUp(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyUp event called of TextBox2");
}
void textBox2_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
listBox1.Items.Add("KeyPress event called of TextBox2");
}
void textBox2_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyDown event called of TextBox2");
}
void textBox2_Enter(object sender, System.EventArgs e)
{
listBox1.Items.Add("Enter event called of TextBox2");
}
Note: To check the exact working of controls use Tab button for GotFocus and LostFocus event and keyboard key stroks for KeyDown, KeyUp, KeyPress events.
To begin with this application create a windows form and drop two textbox control and listbox control. Define the following events for the textbox controls:
Enter Event.
GotFocus Event.
KeyDown Event.
KeyUp Event.
KeyPress Event.
Leave Event.
LostFocus Event.
To check when which occurs I hav used listbox control in which the message is displayed when the respective event will occur. Code for these Events is as follows:
Events for the Textbox control1:
void textBox1_LostFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("LostFocus event called of TextBox1");
}
void textBox1_GotFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("GotFocus event called of TextBox1");
}
void textBox1_Leave(object sender, System.EventArgs e)
{
listBox1.Items.Add("Leave event called of TextBox1");
}
void textBox1_KeyUp(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyUp event called of TextBox1");
}
void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
listBox1.Items.Add("KeyPress event called of TextBox1");
}
void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyDown event called of TextBox1");
}
void textBox1_Enter(object sender, System.EventArgs e)
{
listBox1.Items.Add("Enter event called of TextBox1");
}
Events for the Textbox control2:
void textBox2_LostFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("LostFocus event called of TextBox2");
}
void textBox2_GotFocus(object sender, System.EventArgs e)
{
listBox1.Items.Add("GotFocus event called of TextBox2");
}
void textBox2_Leave(object sender, System.EventArgs e)
{
listBox1.Items.Add("Leave event called of TextBox2");
}
void textBox2_KeyUp(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyUp event called of TextBox2");
}
void textBox2_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
listBox1.Items.Add("KeyPress event called of TextBox2");
}
void textBox2_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
listBox1.Items.Add("KeyDown event called of TextBox2");
}
void textBox2_Enter(object sender, System.EventArgs e)
{
listBox1.Items.Add("Enter event called of TextBox2");
}
Note: To check the exact working of controls use Tab button for GotFocus and LostFocus event and keyboard key stroks for KeyDown, KeyUp, KeyPress events.
Thursday 11 November 2010
Using Paging in Aspx.net with C#
By velmahesh | 11 Nov 2010 | Unedited contribution
How to Implement Using Paging in Aspx.net with C#
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This is a preview of your article
Introduction
How to Implement the code using Paging and Repeater Control in Asp.net with C# .
.aspx Design Page:
To write the Code in Default.aspx page.
Here Used the Repeater Control and LinkButtons.
Page:
Font-Bold="true" runat="server"><%# Container.DataItem %>
.aspx.cs Page:
Then write the code to aspx.cs Page:
First we add the Library Files..
using System.Collections;
using System.Web.UI.HtmlControls;
Then write the Property to Class.. Property Names are FirstIndex,LastIndex,PageNumber. Get and set the values.
public int FirstIndex
{
get
{
if (ViewState["FirstIndex"] != null)
return Convert.ToInt32(ViewState["FirstIndex"]);
else
return 0;
}
set { ViewState["FirstIndex"] = value; }
}
public int LastIndex
{
get
{
if (ViewState["LastIndex"] != null)
return Convert.ToInt32(ViewState["LastIndex"]);
else
return 0;
}
set { ViewState["LastIndex"] = value; }
}
public int PageNumber
{
get
{
if (ViewState["PageNumber"] != null)
return Convert.ToInt32(ViewState["PageNumber"]);
else
return 0;
}
set { ViewState["PageNumber"] = value; }
}
Page Load()
Call the function LoadData() to PageLoad().
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
LoadData();
}
}
LoadData()
Then write the code function name of LoadData()
string keyword = Collections.MySession.keyword;
if (PatApptBiz.SelectModalityName(keyword).Count != 0)
{
List PatAppt = new List();
PatAppt = PatApptBiz.SelectModalityName(keyword);
PagedDataSource pgitems = new PagedDataSource();
pgitems.DataSource = PatAppt;
pgitems.AllowPaging = true;
pgitems.PageSize = 10;
pgitems.CurrentPageIndex = PageNumber;
if (pgitems.PageCount > 0)
{
rptPages.Visible = true;
rptrpopupModalityRoom.Visible = true;
ArrayList pages = new ArrayList();
for (int i = 0; i < pgitems.PageCount; i++)
pages.Add((i + 1).ToString());
ViewState["TotalPages"] = pgitems.PageCount;
this.lblPageTotalInfo.Text = "Page" + (PageNumber + 1) + "of" + pgitems.PageCount;
this.lblPrevPage.Enabled = !pgitems.IsFirstPage;
this.lblNextPage.Enabled = !pgitems.IsLastPage;
this.lblFirstPage.Enabled = !pgitems.IsFirstPage;
this.lblLastPage.Enabled = !pgitems.IsLastPage;
rptPages.DataSource = pages;
rptPages.DataBind();
}
else
rptPages.Visible = false;
// rptrpopupIns.DataSource = refphysicians;
rptrpopupModalityRoom.DataSource = pgitems;
rptrpopupModalityRoom.DataBind();
// Collections.MySession.keyword = null;
}
else
{
lblMsg.Text = "No Records Found..";
this.lblPageTotalInfo.Text = "Page" + (PageNumber + 1) + "of" + (PageNumber + 1);
this.lblPrevPage.Enabled = false;
this.lblNextPage.Enabled = false;
this.lblFirstPage.Enabled = false;
this.lblLastPage.Enabled = false;
rptrpopupModalityRoom.Visible = false;
rptPages.Visible = false;
}
The Events of First, Prev, Next, Last Below:
protected void lblFirstPage_Click(object sender, EventArgs e)
{
PageNumber = 0;
this.LoadData();
}
protected void lblPrevPage_Click(object sender, EventArgs e)
{
PageNumber -= 1;
this.LoadData();
}
protected void lblNextPage_Click(object sender, EventArgs e)
{
PageNumber += 1;
this.LoadData();
}
protected void lblLastPage_Click(object sender, EventArgs e)
{
PageNumber = (Convert.ToInt32(ViewState["TotalPages"]) - 1);
this.LoadData();
}
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
rptPages.ItemCommand += new RepeaterCommandEventHandler(rptrpopupIns_OnItemCommand);
}
Repeater Control with OnItemCommand()
whenever execute OnItemCommand then below function will execute the code.
void rptrpopupIns_OnItemCommand(object source, RepeaterCommandEventArgs e)
{
PageNumber = Convert.ToInt32(e.CommandArgument) - 1;
LoadData();
}
Search button with Text Control
we want the search the items also binding the data to repeater control. so, use the below method..
protected void btnModalitySearch_Click(object sender, EventArgs e)
{
string keyword;
PageNumber = 0;
lblMsg.Text = "";
keyword = txtModalitySearchItem.Text;
Collections.MySession.keyword = keyword;
LoadData()
}
How to Implement Using Paging in Aspx.net with C#
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This is a preview of your article
Introduction
How to Implement the code using Paging and Repeater Control in Asp.net with C# .
.aspx Design Page:
To write the Code in Default.aspx page.
Here Used the Repeater Control and LinkButtons.
Page:
Font-Bold="true" runat="server"><%# Container.DataItem %>
.aspx.cs Page:
Then write the code to aspx.cs Page:
First we add the Library Files..
using System.Collections;
using System.Web.UI.HtmlControls;
Then write the Property to Class.. Property Names are FirstIndex,LastIndex,PageNumber. Get and set the values.
public int FirstIndex
{
get
{
if (ViewState["FirstIndex"] != null)
return Convert.ToInt32(ViewState["FirstIndex"]);
else
return 0;
}
set { ViewState["FirstIndex"] = value; }
}
public int LastIndex
{
get
{
if (ViewState["LastIndex"] != null)
return Convert.ToInt32(ViewState["LastIndex"]);
else
return 0;
}
set { ViewState["LastIndex"] = value; }
}
public int PageNumber
{
get
{
if (ViewState["PageNumber"] != null)
return Convert.ToInt32(ViewState["PageNumber"]);
else
return 0;
}
set { ViewState["PageNumber"] = value; }
}
Page Load()
Call the function LoadData() to PageLoad().
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
LoadData();
}
}
LoadData()
Then write the code function name of LoadData()
string keyword = Collections.MySession.keyword;
if (PatApptBiz.SelectModalityName(keyword).Count != 0)
{
List
PatAppt = PatApptBiz.SelectModalityName(keyword);
PagedDataSource pgitems = new PagedDataSource();
pgitems.DataSource = PatAppt;
pgitems.AllowPaging = true;
pgitems.PageSize = 10;
pgitems.CurrentPageIndex = PageNumber;
if (pgitems.PageCount > 0)
{
rptPages.Visible = true;
rptrpopupModalityRoom.Visible = true;
ArrayList pages = new ArrayList();
for (int i = 0; i < pgitems.PageCount; i++)
pages.Add((i + 1).ToString());
ViewState["TotalPages"] = pgitems.PageCount;
this.lblPageTotalInfo.Text = "Page" + (PageNumber + 1) + "of" + pgitems.PageCount;
this.lblPrevPage.Enabled = !pgitems.IsFirstPage;
this.lblNextPage.Enabled = !pgitems.IsLastPage;
this.lblFirstPage.Enabled = !pgitems.IsFirstPage;
this.lblLastPage.Enabled = !pgitems.IsLastPage;
rptPages.DataSource = pages;
rptPages.DataBind();
}
else
rptPages.Visible = false;
// rptrpopupIns.DataSource = refphysicians;
rptrpopupModalityRoom.DataSource = pgitems;
rptrpopupModalityRoom.DataBind();
// Collections.MySession.keyword = null;
}
else
{
lblMsg.Text = "No Records Found..";
this.lblPageTotalInfo.Text = "Page" + (PageNumber + 1) + "of" + (PageNumber + 1);
this.lblPrevPage.Enabled = false;
this.lblNextPage.Enabled = false;
this.lblFirstPage.Enabled = false;
this.lblLastPage.Enabled = false;
rptrpopupModalityRoom.Visible = false;
rptPages.Visible = false;
}
The Events of First, Prev, Next, Last Below:
protected void lblFirstPage_Click(object sender, EventArgs e)
{
PageNumber = 0;
this.LoadData();
}
protected void lblPrevPage_Click(object sender, EventArgs e)
{
PageNumber -= 1;
this.LoadData();
}
protected void lblNextPage_Click(object sender, EventArgs e)
{
PageNumber += 1;
this.LoadData();
}
protected void lblLastPage_Click(object sender, EventArgs e)
{
PageNumber = (Convert.ToInt32(ViewState["TotalPages"]) - 1);
this.LoadData();
}
protected override void OnInit(EventArgs e)
{
base.OnInit(e);
rptPages.ItemCommand += new RepeaterCommandEventHandler(rptrpopupIns_OnItemCommand);
}
Repeater Control with OnItemCommand()
whenever execute OnItemCommand then below function will execute the code.
void rptrpopupIns_OnItemCommand(object source, RepeaterCommandEventArgs e)
{
PageNumber = Convert.ToInt32(e.CommandArgument) - 1;
LoadData();
}
Search button with Text Control
we want the search the items also binding the data to repeater control. so, use the below method..
protected void btnModalitySearch_Click(object sender, EventArgs e)
{
string keyword;
PageNumber = 0;
lblMsg.Text = "";
keyword = txtModalitySearchItem.Text;
Collections.MySession.keyword = keyword;
LoadData()
}
Tuesday 9 November 2010
C# Interview Questions
C# Interview Questions.
Please Check out the following Links.
http://www.toqc.com/entropy/TheAnswers1.html
http://www.toqc.com/entropy/TheAnswers2.html
http://www.hanselman.com/blog/ASPNETInterviewQuestions.aspx
http://www.hanselman.com/blog/WhatAGreatNETDevelopersOughtToKnowMoreNETInterviewQuestions.aspx
http://www.techinterviews.com/?p=153
Please Check out the following Links.
http://www.toqc.com/entropy/TheAnswers1.html
http://www.toqc.com/entropy/TheAnswers2.html
http://www.hanselman.com/blog/ASPNETInterviewQuestions.aspx
http://www.hanselman.com/blog/WhatAGreatNETDevelopersOughtToKnowMoreNETInterviewQuestions.aspx
http://www.techinterviews.com/?p=153
C# Interview Question And Answers
1. Does C# support multiple-inheritance?
No.
2. Who is a protected class-level variable available to?
It is available to any sub-class (a class inheriting this class).
3. Are private class-level variables inherited?
Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
4. Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.
5. What’s the top .NET class that everything is derived from?
System.Object.
6. What does the term immutable mean?
The data value may not be changed. Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
7. What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable. System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
8. What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.
9. Can you store multiple data types in System.Array?
No.
10. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element’s object, resulting in a different, yet identacle object.
11. How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
12. What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.
13. What class is underneath the SortedList class?
A sorted HashTable.
14. Will the finally block get executed if an exception has not occurred?¬
Yes.
15. What’s the C# syntax to catch any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
16. Can multiple catch blocks be executed for a single try statement?
No. Once the proper catch block processed, control is transferred to the finally block (if there are any).
17. Explain the three services model commonly know as a three-tier application.
Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
Class Questions
1. What is the syntax to inherit from a class in C#?
Place a colon and then the name of the base class.
Example: class MyNewClass : MyBaseClass
2. Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.
3. Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.
4. What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
5. When do you absolutely have to declare a class as abstract?
1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.
2. When at least one of the methods in the class is abstract.
6. What is an interface class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes.
7. Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public, and are therefore public by default.
8. Can you inherit multiple interfaces?
Yes. .NET does support multiple interfaces.
9. What happens if you inherit multiple interfaces and they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
To Do: Investigate
10. What’s the difference between an interface and abstract class?
In an interface class, all methods are abstract – there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
11. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
Method and Property Questions
1. What’s the implicit name of the parameter that gets passed into the set method/property of a class?
Value. The data type of the value parameter is defined by whatever data type the property is declared as.
2. What does the keyword “virtual” declare for a method or property?
The method or property can be overridden.
3. How is method overriding different from method overloading?
When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.
4. Can you declare an override method to be static if the original method is not static?
No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)
5. What are the different ways a method can be overloaded?
Different parameter data types, different number of parameters, different order of parameters.
6. If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
Events and Delegates
1. What’s a delegate?
A delegate object encapsulates a reference to a method.
2. What’s a multicast delegate?
A delegate that has multiple handlers assigned to it. Each assigned handler (method) is called.
XML Documentation Questions
1. Is XML case-sensitive?
Yes.
2. What’s the difference between // comments, /* */ comments and /// comments?
Single-line comments, multi-line comments, and XML documentation comments.
3. How do you generate documentation from the C# file commented properly with a command-line compiler?
Compile it with the /doc switch.
Debugging and Testing Questions
1. What debugging tools come with the .NET SDK?
1. CorDBG – command-line debugger. To use CorDbg, you must compile the original C# file using the /debug switch.
2. DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR.
2. What does assert() method do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
3. What’s the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
4. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels range from None to Verbose, allowing you to fine-tune the tracing activities.
5. Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
6. How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
7. What are three test cases you should go through in unit testing?
1. Positive test cases (correct data, correct output).
2. Negative test cases (broken or missing data, proper handling).
3. Exception test cases (exceptions are thrown and caught properly).
8. Can you change the value of a variable while debugging a C# application?
Yes. If you are debugging via Visual Studio.NET, just go to Immediate window.
ADO.NET and Database Questions
1. What is the role of the DataReader class in ADO.NET connections?
It returns a read-only, forward-only rowset from the data source. A DataReader provides fast access when a forward-only sequential read is needed.
2. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. OLE-DB.NET is a .NET layer on top of the OLE layer, so it’s not as fastest and efficient as SqlServer.NET.
3. What is the wildcard character in SQL?
Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
4. Explain ACID rule of thumb for transactions.
A transaction must be:
1. Atomic – it is one unit of work and does not dependent on previous and following transactions.
2. Consistent – data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t.
3. Isolated – no transaction sees the intermediate results of the current transaction).
4. Durable – the values persist if the data had been committed even if the system crashes right after.
5. What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and password).
6. Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted?
Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
7. What does the Initial Catalog parameter define in the connection string?
The database name to connect to.
8. What does the Dispose method do with the connection object?
Deletes it from the memory.
To Do: answer better. The current answer is not entirely correct.
9. What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical.
Assembly Questions
1. How is the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
2. What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.
3. What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
4. What namespaces are necessary to create a localized application?
System.Globalization and System.Resources.
5. What is the smallest unit of execution in .NET?
an Assembly.
6. When should you call the garbage collector in .NET?
As a good rule, you should not call the garbage collector. However, you could call the garbage collector when you are done using a large object (or set of objects) to force the garbage collector to dispose of those very large objects from memory. However, this is usually not a good practice.
7. How do you convert a value-type to a reference-type?
Use Boxing.
8. What happens in memory when you Box and Unbox a value-type?
Boxing converts a value-type to a reference-type, thus storing the object on the heap. Unboxing converts a reference-type to a value-type, thus storing the value on the stack.
1. Explain the differences between Server-side and Client-side code?
ANS: Server side code will execute at server end all the business logic will execute at server end where as client side code will execute at client side at browser end.
2. What type of code (server or client) is found in a Code-Behind class?
ANS : Server side.
3. Should validation (did the user enter a real date) occur server-side or client-side? Why?
ANS : client side . there is no need to go to validate user input. If it relates to data base validation we need to validate at server side.
4. What does the “EnableViewState” property do? Why would I want it on or off?
ANS: IT keeps the data of the control during post backs.
if we turn off the values should not populate during server round trip.
5. What is the difference between Server.Transfer and
Response.Redirect? Why would I choose one over the other?
ANS: Server.Trnasfer will prevent round trip. it will redirect pages which or in the same directory. NO way to pass the query strings . Thru http context we can able to get the previous page control values.
Response.Redirect : There is a round trip to process the request. We can redirect to any page external / internal other than aspx. We can pass the query string thru which we can manage sessions.
6. Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component
ANS : Web services are best suite for Hetrogenious environment.
Remoting is best suite for Homogenious environment. The systems that under CLR.
7. Let’s say I have an existing application written using Visual Studio 6 (VB 6, InterDev 6) and this application utilizes Windows 2000 COM+ transaction services. How would you approach migrating this
application to .NET
We need to have Wrapper to communicate COM components in .net. and vis versa
CCW : Com Callable wrapper.
RCW : RUN time callable wrapper.
8. Can you explain the difference between an ADO.NET Dataset and anADO Recordset?\
ANS : DIsconnected architechure . Maintainace relation schemas. MUtilple table grouping.
Connected one .
9. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?
ANS: APplication_start need for global variable which are available over the application.
Sesssion_Start : login dependent ( user dependent)
10. If I’m developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is
spanned across three web-servers (using round-robbin load balancing)
what would be the best approach to maintain login-in state for the
users?
ANS : Database Support.
or Thru state service.
11. What are ASP.NET Web Forms? How is this technology different than what is available though ASP (1.0-3.0)?
ANS : ASP . Interprepter.. use the script engine.
ASP.Net Compiled.
12. How does VB.NET/C# achieve polymorphism?
ANS : Function overloading.
Operator overloading.
11. Can you explain what inheritance is and an example of when you might use it?
ANS : Heridity.
Use the existing functionality along with its own properities.
13. How would you implement inheritance using VB.NET/C#?
ANS: Derived Class : Basecalss
VB.NEt : Derived Class Inherits Baseclass
14. Whats an assembly
ANS : A Basic unit of executable code >
Which contains : Manifest – Meta data
versioning , Calture , IL, Reference
15. Describe the difference between inline and code behind – which is best in a loosely coupled solution
Tightly coupled – INLINE
ANS: inline function bind at compile time can write in aspx page with in <% %> .
17. Explain what a diffgram is, and a good use for one
ANS : is an xml grammer. it talk about state of node in xml file.
18. Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one
ANS: Preprocessing before going to IIS.
20. What are the disadvantages of viewstate/what are the benefits
ANS : IT can be hacked . page is size is heavy.
21 Describe session handling in a webfarm, how does it work and what are the limits
ANS:
Session – mode
State sever
OUtprocess
sql
22. How would you get ASP.NET running in Apache web servers – why would you even do this?
ANS: —- Install Mod_AspDotNet
Add at the end of C:\Program Files\Apache Group\Apache2\conf\httpd.conf the following lines
23. Whats MSIL, and why should my developers need an appreciation of it if at all?
ANS : Microsoft Intermeidate lanaguage. which is the out put for all the .net supported languages after comiplation will produce.
Appreciation for cross language support.
24. In what order do the events of an ASPX page execute. As a developer is it important to undertsand these events?
ANS : INIT, PageLoad, Prerender , UNload.
25. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
Fill()
26. Can you edit data in the Repeater control?
NO
27. Which template must you provide, in order to display data in a Repeater control?
ITemtemplate
28. How can you provide an alternating color scheme in a Repeatercontrol?
AlternateItemTemplate
29. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeatercontrol?
Datasource,
DataBind
30. What base class do all Web Forms inherit from?
System.Web.UI.Page
31. What method do you use to explicitly kill a user s session?
abondon()
32 How do you turn off cookies for one page in your site?
disablecookies.
33. Which two properties are on every validation control?
control to validate, error message
34. What tags do you need to add within the asp:datagrid tags to bind
columns manually?
autogenerated columns is set to false
35. How do you create a permanent cookie?
Cooke = ne cookee().
cooke.adddate.
36. What tag do you use to add a hyperlink column to the DataGrid?
hyper link column
37. What is the standard you use to wrap up a call to a Web service
————
38. Which method do you use to redirect the user to another page without performing a round trip to the client?
server.transfer
39. What is the transport protocol you use to call a Web service SOAP
http
40. True or False: A Web service can only be written in .NET
false
41. What does WSDL stand for? webservice discription language. it is used to generate for proxy( server object)
42. What property do you have to set to tell the grid which page to go to when using the Pager object?
Page Index.
43. Where on the Internet would you look for Web services?
UDDI
44. What tags do you need to add within the asp:datagrid tags to bind columns manually.
Autogenerate columns
45. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
datatext
datavalue
46. How is a property designated as read-only?
get
47. Which control would you use if you needed to make sure the values in two different controls matched?
compare filed validator
48. True or False: To test a Web service you must create a windows application or Web application to consume this service?
no
49. How many classes can a single .NET DLL contain?
as many as u want..
No.
2. Who is a protected class-level variable available to?
It is available to any sub-class (a class inheriting this class).
3. Are private class-level variables inherited?
Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
4. Describe the accessibility modifier “protected internal”.
It is available to classes that are within the same assembly and derived from the specified base class.
5. What’s the top .NET class that everything is derived from?
System.Object.
6. What does the term immutable mean?
The data value may not be changed. Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
7. What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable. System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
8. What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.
9. Can you store multiple data types in System.Array?
No.
10. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element’s object, resulting in a different, yet identacle object.
11. How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
12. What’s the .NET collection class that allows an element to be accessed using a unique key?
HashTable.
13. What class is underneath the SortedList class?
A sorted HashTable.
14. Will the finally block get executed if an exception has not occurred?¬
Yes.
15. What’s the C# syntax to catch any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
16. Can multiple catch blocks be executed for a single try statement?
No. Once the proper catch block processed, control is transferred to the finally block (if there are any).
17. Explain the three services model commonly know as a three-tier application.
Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
Class Questions
1. What is the syntax to inherit from a class in C#?
Place a colon and then the name of the base class.
Example: class MyNewClass : MyBaseClass
2. Can you prevent your class from being inherited by another class?
Yes. The keyword “sealed” will prevent the class from being inherited.
3. Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed.
4. What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
5. When do you absolutely have to declare a class as abstract?
1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.
2. When at least one of the methods in the class is abstract.
6. What is an interface class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes.
7. Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public, and are therefore public by default.
8. Can you inherit multiple interfaces?
Yes. .NET does support multiple interfaces.
9. What happens if you inherit multiple interfaces and they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
To Do: Investigate
10. What’s the difference between an interface and abstract class?
In an interface class, all methods are abstract – there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
11. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
Method and Property Questions
1. What’s the implicit name of the parameter that gets passed into the set method/property of a class?
Value. The data type of the value parameter is defined by whatever data type the property is declared as.
2. What does the keyword “virtual” declare for a method or property?
The method or property can be overridden.
3. How is method overriding different from method overloading?
When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.
4. Can you declare an override method to be static if the original method is not static?
No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)
5. What are the different ways a method can be overloaded?
Different parameter data types, different number of parameters, different order of parameters.
6. If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
Events and Delegates
1. What’s a delegate?
A delegate object encapsulates a reference to a method.
2. What’s a multicast delegate?
A delegate that has multiple handlers assigned to it. Each assigned handler (method) is called.
XML Documentation Questions
1. Is XML case-sensitive?
Yes.
2. What’s the difference between // comments, /* */ comments and /// comments?
Single-line comments, multi-line comments, and XML documentation comments.
3. How do you generate documentation from the C# file commented properly with a command-line compiler?
Compile it with the /doc switch.
Debugging and Testing Questions
1. What debugging tools come with the .NET SDK?
1. CorDBG – command-line debugger. To use CorDbg, you must compile the original C# file using the /debug switch.
2. DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR.
2. What does assert() method do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
3. What’s the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
4. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels range from None to Verbose, allowing you to fine-tune the tracing activities.
5. Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
6. How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
7. What are three test cases you should go through in unit testing?
1. Positive test cases (correct data, correct output).
2. Negative test cases (broken or missing data, proper handling).
3. Exception test cases (exceptions are thrown and caught properly).
8. Can you change the value of a variable while debugging a C# application?
Yes. If you are debugging via Visual Studio.NET, just go to Immediate window.
ADO.NET and Database Questions
1. What is the role of the DataReader class in ADO.NET connections?
It returns a read-only, forward-only rowset from the data source. A DataReader provides fast access when a forward-only sequential read is needed.
2. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. OLE-DB.NET is a .NET layer on top of the OLE layer, so it’s not as fastest and efficient as SqlServer.NET.
3. What is the wildcard character in SQL?
Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
4. Explain ACID rule of thumb for transactions.
A transaction must be:
1. Atomic – it is one unit of work and does not dependent on previous and following transactions.
2. Consistent – data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t.
3. Isolated – no transaction sees the intermediate results of the current transaction).
4. Durable – the values persist if the data had been committed even if the system crashes right after.
5. What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and password).
6. Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted?
Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
7. What does the Initial Catalog parameter define in the connection string?
The database name to connect to.
8. What does the Dispose method do with the connection object?
Deletes it from the memory.
To Do: answer better. The current answer is not entirely correct.
9. What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical.
Assembly Questions
1. How is the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
2. What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.
3. What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
4. What namespaces are necessary to create a localized application?
System.Globalization and System.Resources.
5. What is the smallest unit of execution in .NET?
an Assembly.
6. When should you call the garbage collector in .NET?
As a good rule, you should not call the garbage collector. However, you could call the garbage collector when you are done using a large object (or set of objects) to force the garbage collector to dispose of those very large objects from memory. However, this is usually not a good practice.
7. How do you convert a value-type to a reference-type?
Use Boxing.
8. What happens in memory when you Box and Unbox a value-type?
Boxing converts a value-type to a reference-type, thus storing the object on the heap. Unboxing converts a reference-type to a value-type, thus storing the value on the stack.
1. Explain the differences between Server-side and Client-side code?
ANS: Server side code will execute at server end all the business logic will execute at server end where as client side code will execute at client side at browser end.
2. What type of code (server or client) is found in a Code-Behind class?
ANS : Server side.
3. Should validation (did the user enter a real date) occur server-side or client-side? Why?
ANS : client side . there is no need to go to validate user input. If it relates to data base validation we need to validate at server side.
4. What does the “EnableViewState” property do? Why would I want it on or off?
ANS: IT keeps the data of the control during post backs.
if we turn off the values should not populate during server round trip.
5. What is the difference between Server.Transfer and
Response.Redirect? Why would I choose one over the other?
ANS: Server.Trnasfer will prevent round trip. it will redirect pages which or in the same directory. NO way to pass the query strings . Thru http context we can able to get the previous page control values.
Response.Redirect : There is a round trip to process the request. We can redirect to any page external / internal other than aspx. We can pass the query string thru which we can manage sessions.
6. Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component
ANS : Web services are best suite for Hetrogenious environment.
Remoting is best suite for Homogenious environment. The systems that under CLR.
7. Let’s say I have an existing application written using Visual Studio 6 (VB 6, InterDev 6) and this application utilizes Windows 2000 COM+ transaction services. How would you approach migrating this
application to .NET
We need to have Wrapper to communicate COM components in .net. and vis versa
CCW : Com Callable wrapper.
RCW : RUN time callable wrapper.
8. Can you explain the difference between an ADO.NET Dataset and anADO Recordset?\
ANS : DIsconnected architechure . Maintainace relation schemas. MUtilple table grouping.
Connected one .
9. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?
ANS: APplication_start need for global variable which are available over the application.
Sesssion_Start : login dependent ( user dependent)
10. If I’m developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is
spanned across three web-servers (using round-robbin load balancing)
what would be the best approach to maintain login-in state for the
users?
ANS : Database Support.
or Thru state service.
11. What are ASP.NET Web Forms? How is this technology different than what is available though ASP (1.0-3.0)?
ANS : ASP . Interprepter.. use the script engine.
ASP.Net Compiled.
12. How does VB.NET/C# achieve polymorphism?
ANS : Function overloading.
Operator overloading.
11. Can you explain what inheritance is and an example of when you might use it?
ANS : Heridity.
Use the existing functionality along with its own properities.
13. How would you implement inheritance using VB.NET/C#?
ANS: Derived Class : Basecalss
VB.NEt : Derived Class Inherits Baseclass
14. Whats an assembly
ANS : A Basic unit of executable code >
Which contains : Manifest – Meta data
versioning , Calture , IL, Reference
15. Describe the difference between inline and code behind – which is best in a loosely coupled solution
Tightly coupled – INLINE
ANS: inline function bind at compile time can write in aspx page with in <% %> .
17. Explain what a diffgram is, and a good use for one
ANS : is an xml grammer. it talk about state of node in xml file.
18. Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one
ANS: Preprocessing before going to IIS.
20. What are the disadvantages of viewstate/what are the benefits
ANS : IT can be hacked . page is size is heavy.
21 Describe session handling in a webfarm, how does it work and what are the limits
ANS:
Session – mode
State sever
OUtprocess
sql
22. How would you get ASP.NET running in Apache web servers – why would you even do this?
ANS: —- Install Mod_AspDotNet
Add at the end of C:\Program Files\Apache Group\Apache2\conf\httpd.conf the following lines
23. Whats MSIL, and why should my developers need an appreciation of it if at all?
ANS : Microsoft Intermeidate lanaguage. which is the out put for all the .net supported languages after comiplation will produce.
Appreciation for cross language support.
24. In what order do the events of an ASPX page execute. As a developer is it important to undertsand these events?
ANS : INIT, PageLoad, Prerender , UNload.
25. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
Fill()
26. Can you edit data in the Repeater control?
NO
27. Which template must you provide, in order to display data in a Repeater control?
ITemtemplate
28. How can you provide an alternating color scheme in a Repeatercontrol?
AlternateItemTemplate
29. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeatercontrol?
Datasource,
DataBind
30. What base class do all Web Forms inherit from?
System.Web.UI.Page
31. What method do you use to explicitly kill a user s session?
abondon()
32 How do you turn off cookies for one page in your site?
disablecookies.
33. Which two properties are on every validation control?
control to validate, error message
34. What tags do you need to add within the asp:datagrid tags to bind
columns manually?
autogenerated columns is set to false
35. How do you create a permanent cookie?
Cooke = ne cookee().
cooke.adddate.
36. What tag do you use to add a hyperlink column to the DataGrid?
hyper link column
37. What is the standard you use to wrap up a call to a Web service
————
38. Which method do you use to redirect the user to another page without performing a round trip to the client?
server.transfer
39. What is the transport protocol you use to call a Web service SOAP
http
40. True or False: A Web service can only be written in .NET
false
41. What does WSDL stand for? webservice discription language. it is used to generate for proxy( server object)
42. What property do you have to set to tell the grid which page to go to when using the Pager object?
Page Index.
43. Where on the Internet would you look for Web services?
UDDI
44. What tags do you need to add within the asp:datagrid tags to bind columns manually.
Autogenerate columns
45. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
datatext
datavalue
46. How is a property designated as read-only?
get
47. Which control would you use if you needed to make sure the values in two different controls matched?
compare filed validator
48. True or False: To test a Web service you must create a windows application or Web application to consume this service?
no
49. How many classes can a single .NET DLL contain?
as many as u want..
Object Oriented Programming with C#
What is the difference between struct and class in C#?
Structs vs classes in C#
Structs may seem similar to classes, but there are important differences that you should be aware of. First of all, classes are reference types and structs are value types. By using structs, you can create objects that behave like the built-in types and enjoy their benefits as well.
* When you call the New operator on a class, it will be allocated on the heap. However, when you instantiate a struct, it gets created on the stack. This will yield performance gains. Also, you will not be dealing with references to an instance of a struct as you would with classes. You will be working directly with the struct instance. Because of this, when passing a struct to a method, it’s passed by value instead of as a reference.
* Structs can declare constructors, but they must take parameters. It is an error to declare a default (parameterless) constructor for a struct. Struct members cannot have initializers. A default constructor is always provided to initialize the struct members to their default values.
How do I call one constructor from another in C#?
You use : base (parameters) or : this (parameters) just before the actual code for the constructor, depending on whether you want to call a constructor in the base class or in this class.
What is the difference between indexers and properties in C#?
Comparison Between Properties and Indexers
Indexers are similar to properties. Except for the differences shown in the following , all of the rules defined for property accessors apply to indexer accessors as well.
Properties
Identified by its name.
Accessed through a simple name or a member access.
Can be a static or an instance member.
A get accessor of a property has no parameters.
A set accessor of a property contains the implicit value parameter.
Indexers
Identified by its signature.
Accessed through an element access.
Must be an instance member.
A get accessor of an indexer has the same formal parameter list as the indexer.
A set accessor of an indexer has the same formal parameter list as the indexer, in addition to the value parameter.
Which interface(s) must a class implement in order to support the foreach statement?
Required interface for foreach statement:
A class must implement the IEnumerable and IEnumerator interfaces to support the foreach statement.
Explain Abstract, Sealed, and Static Modifiers in C#.
C# provides many modifiers for use with types and type members. Of these, three can be used with classes: abstract, sealed and static.
abstract
Indicates that a class is to be used only as a base class for other classes. This means that you cannot create an instance of the class directly. Any class derived from it must implement all of its abstract methods and accessors. Despite its name, an abstract class can possess non-abstract methods and properties.
sealed
Specifies that a class cannot be inherited (used as a base class). Note that .NET does not permit a class to be both abstract and sealed.
static
Specifies that a class contains only static members (.NET 2.0).
What’s the difference between override and new in C#?
This is all to do with polymorphism. When a virtual method is called on a reference, the actual type of the object that the reference refers to is used to decide which method implementation to use. When a method of a base class is overridden in a derived class, the version in the derived class is used, even if the calling code didn’t “know” that the object was an instance of the derived class. For instance:
public class Base
{
public virtual void SomeMethod()
{
}
}
public class Derived : Base
{
public override void SomeMethod()
{
}
}
…
Base b = new Derived();
b.SomeMethod();
will end up calling Derived.SomeMethod if that overrides Base.SomeMethod.
Name two ways that you can prevent a class from being instantiated.
Ways to prevent a class from instantiated:
A class cannot be instantiated if it is abstract or if it has a private constructor.
Explain some features of interface in C#.
Comparison of interface with class (interface vs class):
* An interface cannot inherit from a class.
* An interface can inherit from multiple interfaces.
* A class can inherit from multiple interfaces, but only one class.
* Interface members must be methods, properties, events, or indexers.
* All interface members must have public access (the default).
* By convention, an interface name should begin with an uppercase I.
Can an abstract class have non-abstract methods?
An abstract class may contain both abstract and non-abstract methods. But an interface can contain only abstract methods.
How do I use an alias for a namespace or class in C#?
Use the using directive to create an alias for a long namespace or class. You can then use it anywhere you normally would have used that class or namespace. The using alias has a scope within the namespace you declare it in.
Sample code:
// Namespace:
using act = System.Runtime.Remoting.Activation;
// Class:
using list = System.Collections.ArrayList;
…
list l = new list(); // Creates an ArrayList
act.UrlAttribute obj; // Equivalent to System.Runtime.Remoting.Activation.UrlAttribute obj
What type of class cannot be inherited?
A sealed class cannot be inherited. A sealed class is used primarily when the class contains static members. Note that a struct is implicitly sealed; so they cannot be inherited.
What keyword must a derived class use to replace a non-virtual inherited method?
new keyword is used to replace (not override) an inherited method with one of the same name.
What is polymorphism in Object Oriented Programming (OOPS) Languages?
In object-oriented programming, polymorphism is a generic term that means ‘many shapes’. (from the Greek meaning “having multiple forms”). Polymorphism is briefly described as “one interface, many implementations.” polymorphism is a characteristic of being able to assign a different meaning or usage to something in different contexts – specifically, to allow an entity such as a variable, a function, or an object to have more than one form.
There are two types of polymorphism one is compile time polymorphism and the other is run time polymorphism. Compile time polymorphism is functions and operators overloading. Runtime time polymorphism is done using inheritance and virtual functions. Here are some ways how we implement polymorphism in Object Oriented programming languages
Interface and abstract methods
Like in C# or JAVA different classes implement a common interface in different ways; is an example of Runtime polymorphism. The interface defines the abstract member functions (no implementation). In class that implement the interface; we define body of those abstract members according to the requirement. Means single definition in interface but multiple implementation in child classes.
Virtual member functions
Using virtual member functions in an inheritance hierarchy allows run-time selection of the appropriate member function. A virtual function is a member function of the base class and which is redefined by the derived class. Such functions can have different implementations that are invoked by a run-time determination of the subtype (virtual method invocation, dynamic binding).
Function Overloading
Polymorphism means that functions assume different forms at different times. In case of compile time it is called function overloading.Two or more functions can have same name but their parameter list should be different either in terms of parameters or their data types. The functions which differ only in their return types cannot be overloaded. The compiler will select the right function depending on the type of parameters passed.
Operator Overloading
In polymorphism operators can also be overloaded (Compile time polymorphism). Operators can be overloaded in order to perform special functions with respect to the class. With the help of operator overloading standard operations such as + , – , * , etc can be applied on the objects of the class.
What is a Virtual Functions in class?
A virtual function is a member function of the base class and which is redefined by the derived class. When a derived class inherits the class containing the virtual function, it has ability to redefine the virtual functions.
A virtual function has a different functionality in the derived class according to the requirement. The virtual function within the base class provides the form of the interface to the function. Virtual function implements the philosophy of one interface and multiple methods (polymorphism).
The virtual functions are resolved at the run time. This is called dynamic binding. The functions which are not virtual are resolved at compile time which is called static binding. A virtual function is created using the keyword virtual which precedes the name of the function.
What is Encapsulation in Object Oriented Programming (OOPS) Languages?
Encapsulation is the procedure of covering up of data and functions into a single unit. Encapsulation (also information hiding) consists of separating the external aspects of an object which are accessible to other objects, from the internal implementation details of the object, which are hidden from other objects.
A process, encapsulation means the act of enclosing one or more items within a (physical or logical) container (Class).
Object-oriented programming is based on encapsulation. When an objects state and behavior are kept together, they are encapsulated. That is, the data that represents the state of the object and the methods (Functions and Subs) that manipulate that data are stored together as a cohesive unit.
The object takes requests from other client objects, but does not expose its the details of its data or code to them. The object alone is responsible for its own state, exposing public messages for clients, and declaring private methods that make up its implementation. The client depends on the (hopefully) simple public interface, and does not know about or depend on the details of the implementation.
For example, a HashTable object will take get() and set() requests from other objects, but does not expose its internal hash table data structures or the code strategies that it uses.
Explain the advantages of Encapsulation in Object Oriented Programming Languages.
Benefits of Encapsulation in oops:
Encapsulation makes it possible to separate an objects implementation from its behavior to restrict access to its internal data. This restriction allows certain details of an objects behavior to be hidden. It allows us to create a “black box” and protects an objects internal state from corruption by its clients.
Encapsulation is a technique for minimizing interdependencies among modules by defining a strict external interface. This way, internal coding can be changed without affecting the interface, so long as the new implementation supports the same (or upwards compatible) external interface. So encapsulation prevents a program from becoming so interdependent that a small change has massive ripple effects.
The implementation of an object can be changed without affecting the application that uses it for: Improving performance, fix a bug, consolidate code or for porting.
Limitations and Restrictions of Interface
The essential idea to remember is that an interface never contains any implementation. The following restrictions and imitations are natural consequences of this:
You’re not allowed any fields in an interface, not even static ones. A field is an implementation of an object attribute.
You’re not allowed any constructors in an interface. A constructor contains the statements used to initialize the fields in an object, and an interface does not contain any fields!
You’re not allowed a destructor in an interface. A destructor contains the statements used to destroy an object instance.
You cannot supply an access modifier. All methods in an interface are implicitly public.
You cannot nest any types (enums, structs, classes, interfaces, or delegates) inside an interface.
What is an Object?
An object is an instance of a class. It can be uniquely identified by its name and it defines a state which is represented by the values of its attributes at a particular time.
An object can be considered a “thing” that can perform a set of activities. The set of activities that the object performs defines the object’s behavior.
The state of the object changes according to the methods which are applied to it. We refer to these possible sequences of state changes as the behavior of the object. So the behavior of an object is defined by the set of methods which can be applied on it.
Objects can communicate by passing messages to each other.
What is inheritance?
Inheritance is the mechanism which allows a class A to inherit properties of a class B. We say “A inherits from B”. Objects of class A thus have access to attributes and methods of class B without the need to redefine them.
If class A inherits from class B, then B is called superclass of A. A is called subclass of B. Objects of a subclass can be used where objects of the corresponding superclass are expected. This is due to the fact that objects of the subclass share the same behavior as objects of the superclass.
However, subclasses are not limited to the state and behaviors provided to them by their superclass. Subclasses can add variables and methods to the ones they inherit from the superclass.
In the literature you may also find other terms for “superclass” and “subclass”. Superclasses are also called parent classes or base classes. Subclasses may also be called child classes or just derived classes.
Inheritance Example
Like a car, truck or motorcycles have certain common characteristics- they all have wheels, engines and brakes. Hence they all could be represented by a common class Vehicle which encompasses all those attributes and methods that are common to all types of vehicles.
However they each have their own unique attributes; car has 4 wheels and is smaller is size to a truck; whereas a motorcycle has 2 wheels. Thus we see a parent-child type of relationship here where the Car, Truck or Motorcycle can inherit certain Characteristics from the parent Vehicle; at the same time having their own unique attributes. This forms the basis of inheritance; Vehicle is the Parent, Super or the Base class. Car, Truck and Motorcycle become the Child, Sub or the Derived class.
Explain some characteristics of inheritance.
A class inherits the members of its direct base class. Inheritance means that a class implicitly contains all members of its direct base class, except for the constructors and destructors of the base class.
Some important aspects of inheritance are:
Inheritance is transitive. If C is derived from B, and B is derived from A, then C inherits the members declared in B as well as the members declared in A.
A derived class extends its direct base class. A derived class can add new members to those it inherits, but it cannot remove the definition of an inherited member.
Constructors and destructors are not inherited, but all other members are, regardless of their declared accessibility. However, depending on their declared accessibility, inherited members might not be accessible in a derived class.
A derived class can hide inherited members by declaring new members with the same name or signature. Note however that hiding an inherited member does not remove that member; it merely makes that member inaccessible in the derived class.
An instance of a class contains a set of all instance fields declared in the class and its base classes, and an implicit conversion exists from a derived class type to any of its base class types. Thus, a reference to an instance of some derived class can be treated as a reference to an instance of any of its base classes.
A class can declare virtual methods, properties, and indexers, and derived classes can override the implementation of these function members. This enables classes to exhibit polymorphic behavior wherein the actions performed by a function member invocation varies depending on the run-time type of the instance through which that function member is invoked.
Structs vs classes in C#
Structs may seem similar to classes, but there are important differences that you should be aware of. First of all, classes are reference types and structs are value types. By using structs, you can create objects that behave like the built-in types and enjoy their benefits as well.
* When you call the New operator on a class, it will be allocated on the heap. However, when you instantiate a struct, it gets created on the stack. This will yield performance gains. Also, you will not be dealing with references to an instance of a struct as you would with classes. You will be working directly with the struct instance. Because of this, when passing a struct to a method, it’s passed by value instead of as a reference.
* Structs can declare constructors, but they must take parameters. It is an error to declare a default (parameterless) constructor for a struct. Struct members cannot have initializers. A default constructor is always provided to initialize the struct members to their default values.
How do I call one constructor from another in C#?
You use : base (parameters) or : this (parameters) just before the actual code for the constructor, depending on whether you want to call a constructor in the base class or in this class.
What is the difference between indexers and properties in C#?
Comparison Between Properties and Indexers
Indexers are similar to properties. Except for the differences shown in the following , all of the rules defined for property accessors apply to indexer accessors as well.
Properties
Identified by its name.
Accessed through a simple name or a member access.
Can be a static or an instance member.
A get accessor of a property has no parameters.
A set accessor of a property contains the implicit value parameter.
Indexers
Identified by its signature.
Accessed through an element access.
Must be an instance member.
A get accessor of an indexer has the same formal parameter list as the indexer.
A set accessor of an indexer has the same formal parameter list as the indexer, in addition to the value parameter.
Which interface(s) must a class implement in order to support the foreach statement?
Required interface for foreach statement:
A class must implement the IEnumerable and IEnumerator interfaces to support the foreach statement.
Explain Abstract, Sealed, and Static Modifiers in C#.
C# provides many modifiers for use with types and type members. Of these, three can be used with classes: abstract, sealed and static.
abstract
Indicates that a class is to be used only as a base class for other classes. This means that you cannot create an instance of the class directly. Any class derived from it must implement all of its abstract methods and accessors. Despite its name, an abstract class can possess non-abstract methods and properties.
sealed
Specifies that a class cannot be inherited (used as a base class). Note that .NET does not permit a class to be both abstract and sealed.
static
Specifies that a class contains only static members (.NET 2.0).
What’s the difference between override and new in C#?
This is all to do with polymorphism. When a virtual method is called on a reference, the actual type of the object that the reference refers to is used to decide which method implementation to use. When a method of a base class is overridden in a derived class, the version in the derived class is used, even if the calling code didn’t “know” that the object was an instance of the derived class. For instance:
public class Base
{
public virtual void SomeMethod()
{
}
}
public class Derived : Base
{
public override void SomeMethod()
{
}
}
…
Base b = new Derived();
b.SomeMethod();
will end up calling Derived.SomeMethod if that overrides Base.SomeMethod.
Name two ways that you can prevent a class from being instantiated.
Ways to prevent a class from instantiated:
A class cannot be instantiated if it is abstract or if it has a private constructor.
Explain some features of interface in C#.
Comparison of interface with class (interface vs class):
* An interface cannot inherit from a class.
* An interface can inherit from multiple interfaces.
* A class can inherit from multiple interfaces, but only one class.
* Interface members must be methods, properties, events, or indexers.
* All interface members must have public access (the default).
* By convention, an interface name should begin with an uppercase I.
Can an abstract class have non-abstract methods?
An abstract class may contain both abstract and non-abstract methods. But an interface can contain only abstract methods.
How do I use an alias for a namespace or class in C#?
Use the using directive to create an alias for a long namespace or class. You can then use it anywhere you normally would have used that class or namespace. The using alias has a scope within the namespace you declare it in.
Sample code:
// Namespace:
using act = System.Runtime.Remoting.Activation;
// Class:
using list = System.Collections.ArrayList;
…
list l = new list(); // Creates an ArrayList
act.UrlAttribute obj; // Equivalent to System.Runtime.Remoting.Activation.UrlAttribute obj
What type of class cannot be inherited?
A sealed class cannot be inherited. A sealed class is used primarily when the class contains static members. Note that a struct is implicitly sealed; so they cannot be inherited.
What keyword must a derived class use to replace a non-virtual inherited method?
new keyword is used to replace (not override) an inherited method with one of the same name.
What is polymorphism in Object Oriented Programming (OOPS) Languages?
In object-oriented programming, polymorphism is a generic term that means ‘many shapes’. (from the Greek meaning “having multiple forms”). Polymorphism is briefly described as “one interface, many implementations.” polymorphism is a characteristic of being able to assign a different meaning or usage to something in different contexts – specifically, to allow an entity such as a variable, a function, or an object to have more than one form.
There are two types of polymorphism one is compile time polymorphism and the other is run time polymorphism. Compile time polymorphism is functions and operators overloading. Runtime time polymorphism is done using inheritance and virtual functions. Here are some ways how we implement polymorphism in Object Oriented programming languages
Interface and abstract methods
Like in C# or JAVA different classes implement a common interface in different ways; is an example of Runtime polymorphism. The interface defines the abstract member functions (no implementation). In class that implement the interface; we define body of those abstract members according to the requirement. Means single definition in interface but multiple implementation in child classes.
Virtual member functions
Using virtual member functions in an inheritance hierarchy allows run-time selection of the appropriate member function. A virtual function is a member function of the base class and which is redefined by the derived class. Such functions can have different implementations that are invoked by a run-time determination of the subtype (virtual method invocation, dynamic binding).
Function Overloading
Polymorphism means that functions assume different forms at different times. In case of compile time it is called function overloading.Two or more functions can have same name but their parameter list should be different either in terms of parameters or their data types. The functions which differ only in their return types cannot be overloaded. The compiler will select the right function depending on the type of parameters passed.
Operator Overloading
In polymorphism operators can also be overloaded (Compile time polymorphism). Operators can be overloaded in order to perform special functions with respect to the class. With the help of operator overloading standard operations such as + , – , * , etc can be applied on the objects of the class.
What is a Virtual Functions in class?
A virtual function is a member function of the base class and which is redefined by the derived class. When a derived class inherits the class containing the virtual function, it has ability to redefine the virtual functions.
A virtual function has a different functionality in the derived class according to the requirement. The virtual function within the base class provides the form of the interface to the function. Virtual function implements the philosophy of one interface and multiple methods (polymorphism).
The virtual functions are resolved at the run time. This is called dynamic binding. The functions which are not virtual are resolved at compile time which is called static binding. A virtual function is created using the keyword virtual which precedes the name of the function.
What is Encapsulation in Object Oriented Programming (OOPS) Languages?
Encapsulation is the procedure of covering up of data and functions into a single unit. Encapsulation (also information hiding) consists of separating the external aspects of an object which are accessible to other objects, from the internal implementation details of the object, which are hidden from other objects.
A process, encapsulation means the act of enclosing one or more items within a (physical or logical) container (Class).
Object-oriented programming is based on encapsulation. When an objects state and behavior are kept together, they are encapsulated. That is, the data that represents the state of the object and the methods (Functions and Subs) that manipulate that data are stored together as a cohesive unit.
The object takes requests from other client objects, but does not expose its the details of its data or code to them. The object alone is responsible for its own state, exposing public messages for clients, and declaring private methods that make up its implementation. The client depends on the (hopefully) simple public interface, and does not know about or depend on the details of the implementation.
For example, a HashTable object will take get() and set() requests from other objects, but does not expose its internal hash table data structures or the code strategies that it uses.
Explain the advantages of Encapsulation in Object Oriented Programming Languages.
Benefits of Encapsulation in oops:
Encapsulation makes it possible to separate an objects implementation from its behavior to restrict access to its internal data. This restriction allows certain details of an objects behavior to be hidden. It allows us to create a “black box” and protects an objects internal state from corruption by its clients.
Encapsulation is a technique for minimizing interdependencies among modules by defining a strict external interface. This way, internal coding can be changed without affecting the interface, so long as the new implementation supports the same (or upwards compatible) external interface. So encapsulation prevents a program from becoming so interdependent that a small change has massive ripple effects.
The implementation of an object can be changed without affecting the application that uses it for: Improving performance, fix a bug, consolidate code or for porting.
Limitations and Restrictions of Interface
The essential idea to remember is that an interface never contains any implementation. The following restrictions and imitations are natural consequences of this:
You’re not allowed any fields in an interface, not even static ones. A field is an implementation of an object attribute.
You’re not allowed any constructors in an interface. A constructor contains the statements used to initialize the fields in an object, and an interface does not contain any fields!
You’re not allowed a destructor in an interface. A destructor contains the statements used to destroy an object instance.
You cannot supply an access modifier. All methods in an interface are implicitly public.
You cannot nest any types (enums, structs, classes, interfaces, or delegates) inside an interface.
What is an Object?
An object is an instance of a class. It can be uniquely identified by its name and it defines a state which is represented by the values of its attributes at a particular time.
An object can be considered a “thing” that can perform a set of activities. The set of activities that the object performs defines the object’s behavior.
The state of the object changes according to the methods which are applied to it. We refer to these possible sequences of state changes as the behavior of the object. So the behavior of an object is defined by the set of methods which can be applied on it.
Objects can communicate by passing messages to each other.
What is inheritance?
Inheritance is the mechanism which allows a class A to inherit properties of a class B. We say “A inherits from B”. Objects of class A thus have access to attributes and methods of class B without the need to redefine them.
If class A inherits from class B, then B is called superclass of A. A is called subclass of B. Objects of a subclass can be used where objects of the corresponding superclass are expected. This is due to the fact that objects of the subclass share the same behavior as objects of the superclass.
However, subclasses are not limited to the state and behaviors provided to them by their superclass. Subclasses can add variables and methods to the ones they inherit from the superclass.
In the literature you may also find other terms for “superclass” and “subclass”. Superclasses are also called parent classes or base classes. Subclasses may also be called child classes or just derived classes.
Inheritance Example
Like a car, truck or motorcycles have certain common characteristics- they all have wheels, engines and brakes. Hence they all could be represented by a common class Vehicle which encompasses all those attributes and methods that are common to all types of vehicles.
However they each have their own unique attributes; car has 4 wheels and is smaller is size to a truck; whereas a motorcycle has 2 wheels. Thus we see a parent-child type of relationship here where the Car, Truck or Motorcycle can inherit certain Characteristics from the parent Vehicle; at the same time having their own unique attributes. This forms the basis of inheritance; Vehicle is the Parent, Super or the Base class. Car, Truck and Motorcycle become the Child, Sub or the Derived class.
Explain some characteristics of inheritance.
A class inherits the members of its direct base class. Inheritance means that a class implicitly contains all members of its direct base class, except for the constructors and destructors of the base class.
Some important aspects of inheritance are:
Inheritance is transitive. If C is derived from B, and B is derived from A, then C inherits the members declared in B as well as the members declared in A.
A derived class extends its direct base class. A derived class can add new members to those it inherits, but it cannot remove the definition of an inherited member.
Constructors and destructors are not inherited, but all other members are, regardless of their declared accessibility. However, depending on their declared accessibility, inherited members might not be accessible in a derived class.
A derived class can hide inherited members by declaring new members with the same name or signature. Note however that hiding an inherited member does not remove that member; it merely makes that member inaccessible in the derived class.
An instance of a class contains a set of all instance fields declared in the class and its base classes, and an implicit conversion exists from a derived class type to any of its base class types. Thus, a reference to an instance of some derived class can be treated as a reference to an instance of any of its base classes.
A class can declare virtual methods, properties, and indexers, and derived classes can override the implementation of these function members. This enables classes to exhibit polymorphic behavior wherein the actions performed by a function member invocation varies depending on the run-time type of the instance through which that function member is invoked.
Advanced C# Questions
What’s the advantage of using System.Text.StringBuilder over System.String?
StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
Can you store multiple data types in System.Array?
No.
What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The first one performs a deep copy of the array, the second one is shallow.
How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
What’s the .NET datatype that allows the retrieval of data by a unique key?
HashTable.
What’s class SortedList underneath?
A sorted HashTable.
Will finally block get executed if the exception had not occurred?
Yes.
What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
Can multiple catch blocks be executed?
No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
Why is it a bad idea to throw your own exceptions?
Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
What’s a delegate?
A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
What’s a multicast delegate?
It’s a delegate that points to and eventually fires off several methods.
How’s the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.
What’s a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.
What’s the difference between and XML documentation tag?
Single line code example and multiple-line code example.
Is XML case-sensitive?
Yes, so and are different elements.
What debugging tools come with the .NET SDK?
CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
What does the This window show in the debugger?
It points to the object that’s pointed to by this reference. Object’s instance data is shown.
What does assert() do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
What’s the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
Can you change the value of a variable while debugging a C# application?
Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
What’s the role of the DataReader class in ADO.NET connections?
It returns a read-only dataset from the data source when the command is executed.
What is the wildcard character in SQL?
Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
Why would you use untrusted verificaion?
Web Services might use it, as well as non-Windows applications.
What’s the data provider name to connect to Access database?
Microsoft.Access.
What does Dispose method do with the connection object?
Deletes it from the memory.
What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
Can you store multiple data types in System.Array?
No.
What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The first one performs a deep copy of the array, the second one is shallow.
How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
What’s the .NET datatype that allows the retrieval of data by a unique key?
HashTable.
What’s class SortedList underneath?
A sorted HashTable.
Will finally block get executed if the exception had not occurred?
Yes.
What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
Can multiple catch blocks be executed?
No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
Why is it a bad idea to throw your own exceptions?
Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
What’s a delegate?
A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
What’s a multicast delegate?
It’s a delegate that points to and eventually fires off several methods.
How’s the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.
What’s a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.
What’s the difference between and XML documentation tag?
Single line code example and multiple-line code example.
Is XML case-sensitive?
Yes, so and are different elements.
What debugging tools come with the .NET SDK?
CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
What does the This window show in the debugger?
It points to the object that’s pointed to by this reference. Object’s instance data is shown.
What does assert() do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
What’s the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
Can you change the value of a variable while debugging a C# application?
Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
What’s the role of the DataReader class in ADO.NET connections?
It returns a read-only dataset from the data source when the command is executed.
What is the wildcard character in SQL?
Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
Why would you use untrusted verificaion?
Web Services might use it, as well as non-Windows applications.
What’s the data provider name to connect to Access database?
Microsoft.Access.
What does Dispose method do with the connection object?
Deletes it from the memory.
What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
C# Basic Question and Answers
1. What’s the implicit name of the parameter that gets passed into the class’ set method? Value, and its datatype depends on whatever variable we’re changing.
2. How do you inherit from a class in C#? Place a colon and then the name of the base class. Notice that it’s double colon in C++.
3. Does C# support multiple inheritance? No, use interfaces instead.
4. When you inherit a protected class-level variable, who is it available to? Classes in the same namespace.
5. Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6. Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write? Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8. What’s the top .NET class that everything is derived from? System.Object.
9. How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10. What does the keyword virtual mean in the method definition? The method can be over-ridden.
11. Can you declare the override method static while the original method is non-static? No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12. Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13. Can you prevent your class from being inherited and becoming a base class for some other classes? Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14. Can you allow class to be inherited, but prevent the method from being over-ridden? Yes, just leave the class public and make the method sealed.
15. What’s an abstract class? A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)? When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17. What’s an interface class? It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18. Why can’t you specify the accessibility modifier for methods inside the interface? They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19. Can you inherit multiple interfaces? Yes, why not.
20. And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21. What’s the difference between an interface and abstract class? In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22. How can you overload a method? Different parameter data types, different number of parameters, different order of parameters.
23. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor? Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24. What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
26. Can you store multiple data types in System.Array? No.
27. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
28. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
29. What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
30. What’s class SortedList underneath? A sorted HashTable.
31. Will finally block get executed if the exception had not occurred? Yes.
32. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
33. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
34. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
35. What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
36. What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.
37. How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
38. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
39. What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
40. What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
41. What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
42. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
43. What’s the difference between and XML documentation tag? Single line code example and multiple-line code example.
44. Is XML case-sensitive? Yes, so and are different elements.
45. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
46. What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
47. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
48. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
49. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
50. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
51. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
52. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
53. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
54. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
55. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
56. What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
57. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
58. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
59. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
60. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
61. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
62. What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
63. What’s the data provider name to connect to Access database? Microsoft.Access.
64. What does Dispose method do with the connection object? Deletes it from the memory.
65. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
2. How do you inherit from a class in C#? Place a colon and then the name of the base class. Notice that it’s double colon in C++.
3. Does C# support multiple inheritance? No, use interfaces instead.
4. When you inherit a protected class-level variable, who is it available to? Classes in the same namespace.
5. Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6. Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write? Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8. What’s the top .NET class that everything is derived from? System.Object.
9. How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10. What does the keyword virtual mean in the method definition? The method can be over-ridden.
11. Can you declare the override method static while the original method is non-static? No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12. Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13. Can you prevent your class from being inherited and becoming a base class for some other classes? Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14. Can you allow class to be inherited, but prevent the method from being over-ridden? Yes, just leave the class public and make the method sealed.
15. What’s an abstract class? A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)? When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17. What’s an interface class? It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18. Why can’t you specify the accessibility modifier for methods inside the interface? They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19. Can you inherit multiple interfaces? Yes, why not.
20. And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21. What’s the difference between an interface and abstract class? In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22. How can you overload a method? Different parameter data types, different number of parameters, different order of parameters.
23. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor? Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24. What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25. What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
26. Can you store multiple data types in System.Array? No.
27. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
28. How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.
29. What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
30. What’s class SortedList underneath? A sorted HashTable.
31. Will finally block get executed if the exception had not occurred? Yes.
32. What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
33. Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
34. Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
35. What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
36. What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.
37. How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
38. What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
39. What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
40. What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
41. What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.
42. How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
43. What’s the difference between and XML documentation tag? Single line code example and multiple-line code example.
44. Is XML case-sensitive? Yes, so and are different elements.
45. What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
46. What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
47. What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
48. What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
49. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
50. Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
51. How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
52. What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
53. Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
54. Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
55. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
56. What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
57. What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
58. Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
59. What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
60. Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
61. Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.
62. What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
63. What’s the data provider name to connect to Access database? Microsoft.Access.
64. What does Dispose method do with the connection object? Deletes it from the memory.
65. What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
Interview questions for Csharp
1.What’s the implicit name of the parameter that gets passed into the class’ set method?
Value, and its datatype depends on whatever variable we’re changing.
2.How do you inherit from a class in C#?
Place a colon and then the name of the base class. Notice that it’s double colon in C++.
3.Does C# support multiple inheritance? No, use interfaces instead.
4.When you inherit a protected class-level variable, who is it available to?
Classes in the same namespace.
5.Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6.Describe the accessibility modifier protected internal?
It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7.C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8.What’s the top .NET class that everything is derived from?
System.Object.
9.How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10.What does the keyword virtual mean in the method definition? The method can be over-ridden.
11.Can you declare the override method static while the original method is non-static?
No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12.Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13.Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14.Can you allow class to be inherited, but prevent the method from being over-ridden?
Yes, just leave the class public and make the method sealed.
15.What’s an abstract class?
A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16.When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17.What’s an interface class?
It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18.Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19.Can you inherit multiple interfaces?
Yes, why not.
20.And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21.What’s the difference between an interface and abstract class?
In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22.How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.
23.If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24.What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25.What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
26.Can you store multiple data types in System.Array?
No.
27.What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The first one performs a deep copy of the array, the second one is shallow.
28.How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
29.What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
30.What’s class SortedList underneath?
A sorted HashTable.
31.Will finally block get executed if the exception had not occurred?
Yes.
32.What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
33.Can multiple catch blocks be executed?
No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
34.Why is it a bad idea to throw your own exceptions?
Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
35.What’s a delegate?
A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
36.What’s a multicast delegate?
It’s a delegate that points to and eventually fires off several methods.
37.How’s the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
38.What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.
39.What’s a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
40.What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
41.What’s the difference between // comments, /* */ comments and /// comments?
Single-line, multi-line and XML documentation comments.
42.How do you generate documentation from the C# file commented properly with a command-line compiler?
Compile it with a /doc switch.
43.What’s the difference between c and code XML documentation tag?
Single line code example and multiple-line code example.
44.Is XML case-sensitive?
Yes, so Student and student are different elements.
45.What debugging tools come with the .NET SDK?
CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
46.What does the This window show in the debugger?
It points to the object that’s pointed to by this reference. Object’s instance data is shown.
47.What does assert() do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
48.What’s the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
49.Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
50.Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
51.How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
52.What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
53.Can you change the value of a variable while debugging a C# application?
Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
54.Explain the three services model (three-tier application)?
Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
55.What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
56.What’s the role of the DataReader class in ADO.NET connections?
It returns a read-only dataset from the data source when the command is executed.
57.What is the wildcard character in SQL?
Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
58.Explain ACID rule of thumb for transactions?
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
59.What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
60.Which one is trusted and which one is untrusted?
Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
61.Why would you use untrusted verificaion?
Web Services might use it, as well as non-Windows applications.
62.What does the parameter Initial Catalog define inside Connection String?
The database name to connect to.
63.What’s the data provider name to connect to Access database?
Microsoft.Access.
64.What does Dispose method do with the connection object?
Deletes it from the memory.
What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
Value, and its datatype depends on whatever variable we’re changing.
2.How do you inherit from a class in C#?
Place a colon and then the name of the base class. Notice that it’s double colon in C++.
3.Does C# support multiple inheritance? No, use interfaces instead.
4.When you inherit a protected class-level variable, who is it available to?
Classes in the same namespace.
5.Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.
6.Describe the accessibility modifier protected internal?
It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).
7.C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
8.What’s the top .NET class that everything is derived from?
System.Object.
9.How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
10.What does the keyword virtual mean in the method definition? The method can be over-ridden.
11.Can you declare the override method static while the original method is non-static?
No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
12.Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.
13.Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
14.Can you allow class to be inherited, but prevent the method from being over-ridden?
Yes, just leave the class public and make the method sealed.
15.What’s an abstract class?
A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
16.When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
17.What’s an interface class?
It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
18.Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.
19.Can you inherit multiple interfaces?
Yes, why not.
20.And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
21.What’s the difference between an interface and abstract class?
In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
22.How can you overload a method?
Different parameter data types, different number of parameters, different order of parameters.
23.If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
24.What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
25.What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
26.Can you store multiple data types in System.Array?
No.
27.What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The first one performs a deep copy of the array, the second one is shallow.
28.How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.
29.What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
30.What’s class SortedList underneath?
A sorted HashTable.
31.Will finally block get executed if the exception had not occurred?
Yes.
32.What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception?
A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
33.Can multiple catch blocks be executed?
No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
34.Why is it a bad idea to throw your own exceptions?
Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
35.What’s a delegate?
A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
36.What’s a multicast delegate?
It’s a delegate that points to and eventually fires off several methods.
37.How’s the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
38.What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.
39.What’s a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
40.What namespaces are necessary to create a localized application? System.Globalization, System.Resources.
41.What’s the difference between // comments, /* */ comments and /// comments?
Single-line, multi-line and XML documentation comments.
42.How do you generate documentation from the C# file commented properly with a command-line compiler?
Compile it with a /doc switch.
43.What’s the difference between c and code XML documentation tag?
Single line code example and multiple-line code example.
44.Is XML case-sensitive?
Yes, so Student and student are different elements.
45.What debugging tools come with the .NET SDK?
CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
46.What does the This window show in the debugger?
It points to the object that’s pointed to by this reference. Object’s instance data is shown.
47.What does assert() do?
In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
48.What’s the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
49.Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
50.Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
51.How do you debug an ASP.NET Web application?
Attach the aspnet_wp.exe process to the DbgClr debugger.
52.What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
53.Can you change the value of a variable while debugging a C# application?
Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
54.Explain the three services model (three-tier application)?
Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
55.What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?
SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
56.What’s the role of the DataReader class in ADO.NET connections?
It returns a read-only dataset from the data source when the command is executed.
57.What is the wildcard character in SQL?
Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
58.Explain ACID rule of thumb for transactions?
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
59.What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
60.Which one is trusted and which one is untrusted?
Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
61.Why would you use untrusted verificaion?
Web Services might use it, as well as non-Windows applications.
62.What does the parameter Initial Catalog define inside Connection String?
The database name to connect to.
63.What’s the data provider name to connect to Access database?
Microsoft.Access.
64.What does Dispose method do with the connection object?
Deletes it from the memory.
What is a pre-requisite for connection pooling?
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
Camel case Vs Pascal case
Camel case Also called “mixed case” or “inter case,” this naming convention joins words without using spaces or underscores. The first letter is lowercase, hence the name camel for the hump where an uppercase letter appears. For example, firstName is a variable that uses camel case.
Pascal case Very similar to the camel case, the Pascal case begins with uppercase and then joins words with capital letters. You will find that classes and constructor functions typically use the Pascal case. For example, CustomerList is an example of the Pascal case where two words are joined into one.
Pascal case Very similar to the camel case, the Pascal case begins with uppercase and then joins words with capital letters. You will find that classes and constructor functions typically use the Pascal case. For example, CustomerList is an example of the Pascal case where two words are joined into one.
Model View Controller – MVC – an Intro
Model: The model is, in effect, the application’s business layer. It usually consists of objects that represent the business entities that make up the application, such as customers and products.
View: The view is the application’s user interface. In a Web application, this consists of one or more HTML pages that define the look and feel of the application.
Controller: The controller manages the events processed by the application. The events are usually generated by user-interface actions, such as the user clicking a button or selecting an item from a drop-down list.
View: The view is the application’s user interface. In a Web application, this consists of one or more HTML pages that define the look and feel of the application.
Controller: The controller manages the events processed by the application. The events are usually generated by user-interface actions, such as the user clicking a button or selecting an item from a drop-down list.
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