ASP NET Interview Question and answer (DOC) by nuhman10

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									1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page
   loading process.
   inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other
   things.When an ASP.NET request is received (usually a file with .aspx extension), the
   ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker
   process aspnet_wp.exe.

2. What’s the difference between Response.Write() andResponse.Output.Write()?
   Response.Output.Write() allows you to write formatted output.

3. What methods are fired during the page load?
   Init() - when the page is instantiated
   Load() - when the page is loaded into server memory
   PreRender() - the brief moment before the page is displayed to the user as HTML
   Unload() - when page finishes loading.

4. When during the page processing cycle is ViewState available?
   After the Init() and before the Page_Load(), or OnLoad() for a control.

5. What namespace does the Web page belong in the .NET Framework class

6. Where do you store the information about the user’s locale?

7. What’s the difference between Codebehind="MyCode.aspx.cs"
   CodeBehind is relevant to Visual Studio.NET only.

8. What’s a bubbled event?
   When you have a complex control, like DataGrid, writing an event processing routine for
   each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their
   eventhandlers, allowing the main DataGrid event handler to take care of its constituents.

9. Suppose you want a certain ASP.NET function executed on MouseOver for
   a certain button. Where do you add an event handler?
   Add an OnMouseOver attribute to the button. Example:

10. What data types do the RangeValidator control support?
    Integer, String, and Date.

11. Explain the differences between Server-side and Client-side code?
    Server-side code executes on the server. Client-side code executes in the
   client's browser.

12. What type of code (server or client) is found in a Code-Behind class?
    The answer is server-side code since code-behind is executed on the server. However,
    during the code-behind's execution on the server, it can render client-side code such
    as JavaScript to be processed in the clients browser. But just to be clear, code-behind
    executes on the server, thus making it server-side code.

13. Should user input data validation occur server-side or client-side? Why?
    All user input data validation should occur on the server at a minimum. Additionally,
    client-side validation can be performed where deemed appropriate and feasable to
    provide a richer, more responsive experience for the user.

14. What is the difference between Server.Transfer and Response.Redirect? Why
    would I choose one over the other?
    Server.Transfer transfers page processing from one page directly to the next page without
    making a round-trip back to the client's browser. This provides a faster response with a
    little less overhead on the server. Server.Transfer does not update the clients url
    history list or current url. Response.Redirect is used to redirect the user's browser to
    another page or site. This performas a trip back to the client where the client's browser is
    redirected to the new page. The user's browser history list is updated to reflect the new

15. Can you explain the difference between an ADO.NET Dataset and an ADO
    Valid answers are:
    · A DataSet can represent an entire relational database in memory, complete with tables,
    relations, and views.
    · A DataSet is designed to work without any continuing connection to the original data
    · Data in a DataSet is bulk-loaded, rather than being loaded on demand.
    · There's no concept of cursor types in a DataSet.
    · DataSets have no current record pointer You can use For Each loops to move through
    the data.
    · You can store many edits in a DataSet, and write them to the original data source in a
    single operation.
    · Though the DataSet is universal, other objects in ADO.NET come in different versions
    for different data sources.

16. What is the Global.asax used for?
    The Global.asax (including the Global.asax.cs file) is used to implement application and
    session level events.

17. What are the Application_Start and Session_Start subroutines used for?
    This is where you can set the specific variables for the Application and Session objects.
18. Can you explain what inheritance is and an example of when you might use it?
    When you want to inherit (use the functionality of) another class. Example: With a base
    class named Employee, a Manager class could be derived from the Employee base class.

19. Whats an assembly?
    Assemblies are the building blocks of the .NET framework. Overview of assemblies from

20. Describe the difference between inline and code behind.
    Inline code written along side the html in a page. Code-behind is code written in a
    separate file and referenced by the .aspx page.

21. Explain what a diffgram is, and a good use for one?
    The DiffGram is one of the two XML formats that you can use to render DataSet object
    contents to XML. A good use is reading database data to an XML file to be sent to a
    Web Service.

22. Whats MSIL, and why should my developers need an appreciation of it if at all?
    MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get
    converted to MSIL. MSIL also allows the .NET Framework to JIT compile the assembly
    on the installed computer.

23. Which method do you invoke on the DataAdapter control to load your generated
    dataset with data?
    The Fill() method.

24. Can you edit data in the Repeater control?
    No, it just reads the information from its data source.

25. Which template must you provide, in order to display data in a Repeater control?

26. How can you provide an alternating color scheme in a Repeater control?
    Use the AlternatingItemTemplate.

27. What property must you set, and what method must you call in your code, in order
    to bind the data from a data source to the Repeater control?
    You must set the DataSource property and call the DataBind method.

28. What base class do all Web Forms inherit from?
    The Page class.

29. Name two properties common in every validation control?
    ControlToValidate property and Text property.
  30. 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?
      DataTextField property.

  31. Which control would you use if you needed to make sure the values in two different
      controls matched?
      CompareValidator control.

  32. How many classes can a single .NET DLL contain?
      It can contain many classes.

Web Service Questions

  1. What is the transport protocol you use to call a Web service?
     SOAP (Simple Object Access Protocol) is the preferred protocol.

  2. True or False: A Web service can only be written in .NET?

  3. What does WSDL stand for?
     Web Services Description Language.

  4. Where on the Internet would you look for Web services?

  5. True or False: To test a Web service you must create a Windows application or Web
     application to consume this service?
     False, the web service comes with a test page and it provides HTTP-GET method to test.

State Management Questions

  1. What is ViewState?
     ViewState allows the state of objects (serializable) to be stored in a hidden field on the
     page. ViewState is transported to the client and back to the server, and is not stored on
     the server or any other external source. ViewState is used the retain the state of server-
     side objects between postabacks.

  2. What is the lifespan for items stored in ViewState?
     Item stored in ViewState exist for the life of the current page. This includes postbacks
     (to the same page).

  3. What does the "EnableViewState" property do? Why would I want it on or off?
     It allows the page to save the users input on a form across postbacks. It saves the server-
     side values for a given control into ViewState, which is stored as a hidden value on the
   page before sending the page to the clients browser. When the page is posted back to the
   server the server control is recreated with the state stored in viewstate.

4. What are the different types of Session state management options available with
   ASP.NET provides In-Process and Out-of-Process state management. In-Process stores
   the session in memory on the web server. This requires the a "sticky-server" (or no load-
   balancing) so that the user is always reconnected to the same web server. Out-of-Process
   Session state management stores data in an external data source. The external data
   source may be either a SQL Server or a State Server service. Out-of-Process state
   management requires that all objects stored in session are serializable.
       1) What is CLS (Common Language Specificaiton)?
          It provides the set of specificaiton which has to be adhered by any new language writer
          / Compiler writer for .NET Framework. This ensures Interoperability. For example:
          Within a ASP.NET application written in C#.NET language, we can refer to any DLL
          written in any other language supported by .NET Framework. As of now .NET Supports
          around 32 languages.

           2) What is CTS (Common Type System)?
           It defines about how Objects should be declard, defined and used within .NET. CLS is the
           subset of CTS.

           3) What is Boxing and UnBoxing?
           Boxing is implicit conversion of ValueTypes to Reference Types (Object) .
           UnBoxing is explicit conversion of Reference Types (Object) to its equivalent ValueTypes.
           It requires type-casting.

           4) What is the difference between Value Types and Reference Types?
           Value Types uses Stack to store the data where as the later uses the Heap to store the

           5) What are the different types of assemblies available and their purpose?
           Private, Public/shared and Satellite Assemblies.

           Private Assemblies : Assembly used within an application is known as private assemblies

           Public/shared Assemblies : Assembly which can be shared across applicaiton is known as
           shared assemblies. Strong Name has to be created to create a shared assembly. This can
           be done using SN.EXE. The same has to be registered using GACUtil.exe (Global
           Assembly Cache).

           Satellite Assemblies : These assemblies contain resource files pertaining to a locale
   (Culture+Language). These assemblies are used in deploying an Gloabl applicaiton for
   different languages.

   6) Is String is Value Type or Reference Type in C#?
   String is an object (Reference Type).

1. What is the user in an application?

   2. How can you unload an app without touching the iis?

   3. What is "delegation" in c# ?

   4. in a load balancing environment, which way you choose to maintain state info, if
   security is important?

   5. What is the life cycle of an page? (events, from start to end)

   6. What command line tools do we have in .net environment?

   7. What is the plugin architecture? how to use it?

1. What is the purpose of XSLT other than displaying XML contents in HTML?

   2. How to refresh a static HTML page?

   3. What is the difference between DELETE and TRUNCATE in SQL?

   4. How to declare the XSLT document?

   5. What are the data Islands in XML?

   6. How to initialize COM in ASP?

   7. What are the deferences of DataSet and ???

   8. What are the cursers in ADO?

   9. What are the in-build components in ASP?
10. What are the Objects in ASP?

1.Using ADO.NET Datareader a user extracted data from a database table
having 5 records.What happens if another user adda 5 more
records to the table same time.Can the first user extracted records
become 10 instead of 5 or will it remain same 5?
what about same case when ADO ? pls explain in detail.

2. Using ADO.NET Datareader a user extracts data from a database table
having 1000 rows.He closed his browser in between.
that is after fetching only 50 records.
What happens to the Datareader?will it remain connected?
and will fetch 1000 records and what after?
will garbage collector collect and dispose it soon?

3. A user fetched dtata from a database table
using Dataset(Disconnected records) for updation.
Another user deleted the table just after.
what happens when the first user try to update the table after changes? Error or
Something else?

4. What are different types of assemblies in ASP.NET?

5.where is session id stored in ASP? in IIS aerver or ASP Engine?

When designing an ASCX control is it good practice to use read from the viewstate in
onload event of the control? Why or Why not.

answer: Its not good practice because if the control is loaded in page_load by use of
LoadControl() it will not see any of its own viewstate in onload. So if there is a textbox
on the ascx that the control needs it will not be able to see the postback data.

string temp = textbox1.text

temp = ""
At the end of the onload event it will sync back up with viewstate. So in any of the
userfired events it will have the correct values.

Also anything that is not named or loaded global must be loaded before it will respond
to events on the pages round trip.

If the control is named in the html portion it will have its viewstate synced already in

    1. What is the user in an application?

        2. How can you unload an app without touching the iis?

        3. What is "delegation" in c# ?

        4. in a load balancing environment, which way you choose to maintain state
        info, if security is important?

        5. What is the life cycle of an page? (events, from start to end)

        6. What command line tools do we have in .net environment?

        7. What is the plugin architecture? how to use it?

1. What is HTML ?
2. What is XML ?
3. What is the difference between a class and struct ?
4. What is the difference between a Get and a Post ?
5. What is a managed code ?
6. int n *=2; int x = n & 1; What is the value of x ?
7. What is a friend in C++ ?

1.Why would you use an array vs linked-list ?

Linked List:
? They allow a new element to be inserted or deleted at any position in a constant
number of operations (changing some references) O(1).
? Easy to delete a node (as it only has to rearrange the links to the different nodes).,
? To find the nth node, will need to recurse through the list till it finds [linked lists allow
only sequential access to elements. ], O(n)
               ? Insertion or deletion of element at any position require a linear (O(n)) number of
               ? Poor at deleting nodes (or elements) as it cannot remove one node without
               individually shifting all the elements up the list by one., O(n)
               ? Poor at inserting as an array will eventually either fill up or need to be resized, an
               expensive operation that may not even be possible if memory is fragmented. Similarly,
               an array from which many elements are removed may become wastefully empty or
               need to be made smaller, O(n)

               ? easy to find the nth element in the array by directly referencing them by their position
               in the array.[ arrays allow random access ] , O(1)

               For beginners in the following site is very useful...

               What do you mean by GAC(Global Assembly Cache)?

               what is webservices?How it is work

               1.what are ADO objects int .net?
               2.What is differance between ASP.NET & ASP?
               3.Is .net a platform independent?
               4 What is default datatype in .net?

 Session Never Expired 4/23/2006 11:42 PM Satyadeep
Session Never Expired
On Code Project, I found something very useful in which the author was discussing a very
beautiful idea for preventing session timeouts Idea was to call the following function in the Page
Load() event.
private void ReconnectSession()
int int_MilliSecondsTimeOut = (this.Session.Timeout * 60000) - 30000;
string str_Script = @"
<script type='text/javascript'>
function Reconnect()
window.setInterval('Reconnect()',"+int_MilliSecondsTimeOut.ToString()+ @");
this.Page.RegisterClientScriptBlock("Reconnect", str_Script);
Using the above code the page will restore the session variables 30 seconds prior to session
timeout specified in the web.config file.
What it does is, calling a javascript function that opens a page in a new window. This javascript
function call is "scheduled" so that the it will happen when the session is going to expire in 30
seconds. window.setInterval() is used for that purpose.
In my application, some details were to be retrieved from the database at the time of session
renewal. Reconnect.aspx is the page in which these things are done. You can put your own code
in that page.
In the actual article on Code Project, the author was trying to embed the page within a java script
Image() tag. This was not suitable for my application. So 30 seconds prior to session expiry, I am
opening a window with the above properties and after refreshing the session variables, it will
close automatically. Since that idea is pretty straight forward, we are not discussing it here.
The trickiest part of the game is yet to come. If the application consists of more than 50 or 100
pages, in order to avoid pasting the code in every page, we can make use of the inheritance
feature of web forms.
As we know, all the web forms are inherited from the System.Web.UI.Page class. We can add a
class file to the project that inherits from System.Web.UI.Page class.
public class YourNewPageClass : System.Web.UI.Page

Then add the following code to the class.
override protected void OnInit(EventArgs e)

if (Context.Session != null)
int int_MilliSecondsTimeOut = (this.Session.Timeout * 60000) - 30000;
string str_Script = @"
<script type='text/javascript'>
function Reconnect()
window.setInterval('Reconnect()',"+int_MilliSecondsTimeOut.ToString()+ @");
this.Page.RegisterClientScriptBlock("Reconnect", str_Script);

Solution 2
I recently came across some code which attempted to fix this problem but that was unsuccessful
because the author had forgotten the issue of client side caching.
Add to your page the following code:
private void Page_Load(object sender, System.EventArgs e)
private void AddKeepAlive()
int int_MilliSecondsTimeOut = (this.Session.Timeout * 60000) - 30000;
string str_Script = @"
<script type='text/javascript'>
//Number of Reconnects
var count=0;
//Maximum reconnects setting
var max = 5;
function Reconnect()
if (count < max)
window.status = 'Link to Server Refreshed ' + count.toString()+' time(s)' ;
var img = new Image(1,1);
img.src = 'Reconnect.aspx';
window.setInterval('Reconnect()',"+ _
int_MilliSecondsTimeOut.ToString()+ @"); //Set to length required
this.Page.RegisterClientScriptBlock("Reconnect", str_Script);
This code will cause the client to request within 30 seconds of the session timeout the page

The Important Part
Now this works the first time but if the page is cached locally then the request is not made to the
server and the session times out again, so what we have to do is specify that the page
Reconnect.aspx cannot be cached at the server or client.
This is done by creating the Reconnect.aspx page with this content:
<%@ OutputCache Location="None" VaryByParam="None" %>
The OutputCache directive prevents this from being cached and so the request is made each time.
No code behind file will be needed for this page so no @Page directive is needed either.
What is a proxy in web service? How do I use a proxy server when invoking a Web

What are the events fired when web service called?
How will do transaction in Web Services?
How does SOAP transport happen and what is the role of HTTP in it? How you can
access a webservice using soap?
What are the different formatters can be used in both? Why?.. binary/soap
How you will protect / secure a web service?

1) EnableViewStateMac is designed to detect when the viewstate of a page has been
tampered with. If the EnableViewStateMac attribute of the page directive is set to true
then the server will perform a Machine Authentication Check on the viewstate posted
back to determine if it has been tampered with on the client.

Further, if you perform a Server.Execute() on a page it is important to disable viewstate
mac on the page you are executing else the server will report that the viewstate has
been tampered with (since the page that has been executed' ViewState will be merged
with the Viewstate of the calling page and thus wont match with what the server

2) Bubbling an event is the process of passing an event upto a higher level event handler
to prevent having to write an event handler for each individual object. For example, if
you had lots of buttons on a row, rather than writing a handler for each button you
could bubble the event up to an object higher in the hierarchy to handle. The original
event data should still be available.

3) As you describe a delegate is in essence a pointer to a function. Why use delegates?

A delegate allows you to specify the format of the function that you will be calling
without having to specify which function you wish to call - this then leaves it upto the
function called to determine how to implement the action.

As a practical example: say you wish to design a sort method but are unsure how the
sort should be implemented, you can define a sort delegate which, when called can
notify any subscribers with the correct signature that the data needs to be sorted -
these functions have therefore been "delegated" or assigned with the requirement to
sort data without the original caller having to worry about the implementation -- as long
as the signature (return type and parameters) match the delegate then the
responsibility of performing a sort can be off-loaded to another function.
By seperating the algorithm it allows the code to be written in a more general way.

Think of it like a button you add to a form: onclick you want to notify the application
that a click has occured but you want to offload the responsibility of handling the action
to something else as you dont know how it needs to be implemented.

what is a diffgram?

what are the types of HTML's?

1). what are the event which are there in datagrid for ASP.NET with csharp

2). What are object that can be placed in in datagrid

3). What is code for placing the text box in the datagird

    1) What is a framework?
       2) Why does a ASP.NET web page get compiled twice?
       3) Explain MSIL in terms of PE.
       4) What is a web service? Explain WSDL.

        It is an extremely good to start practising your data structures using C#.

        5) What are the different states of a ASP.NET web page?
        6) What is the difference between jpeg and gif formats?

1) How do you pass by reference rather than by value in C#?

    By default C# passes parameters by value. To make it pass by reference, keywords
    ref and out can be used. Difference between them is that ref parameter needs to be
    initialised, as below

    int itot = 20;

    Add(10, ref itot);

    For out:
    Add(10, out itot);
    No need of initializing the parameter in case of out.

    2) What does the virtual and override keywords mean and how are they used?
When a method, property or event is declared with Virtual keyword, the derived
class can modify and override the method, property or event.
Override keyword is used when a derived class wants to change the functionality of
a method from its actual definitionin the base class.

3) What is MVC?
MVC is a Design method where the Business logic in the application is completely
decoupled from presentation layer logic. this way, it is eaasy to program and also
maintain high profile applications.
MVC = Model View Control

4) What is the Singleton pattern?
Singleton Pattern defines that an object of a class of this type can have only one
instance active at any time and that it provides a Global point of access to it from a
well known access point.

What is View State?
*Can you read the View State?
*What is the difference between encoding and encryption? Which is easy to break?
*Can we disable the view state application wide?
*can we disable it on page wide?
*can we disable it for a control?
*What is provider Model?
*Any idea of Data Access Component provided by Microsoft?
*Any idea of Enterprise library?
*What is web service?
*What is WSDL?
*Can a web service be only developed in asp.ent?
*can we use multiple web services from a single application?
*can we call a web service asynchronously?
*Can a web service be used from a windows application?
*What do we need to deploy a web service?
*What is the significance of web.config?
*Can we have multiple web.config files in a sigle web project?
*Can we have more then one configuration file?
*Type of Authentications?
*Can we have multiple assemblies in a single web project?
*What is GAC?
*What is machine.config?
*What different types of session state Management we have in
*What are cookies?
*What is Cache?
*What is AJAX?
*Is AJAX a language?
*What is the difference between syncronus and asyncronus?
*What is an Assembly?
*Can an assembly contains more then one classes?
*What is strong name?
*What is the difference b/w client and server side?
*What we need for the deployment of a we application?
*what is the purpose of IIS?
*Difference between http and https?
*what is purpose of aspnet_wp.exe ?
*what is an ISAPI filter?
*what do you mean by HTTP Handler?
*What is the purpose of Global.asax?
*What is the significance of Application_Start/Session_Start/Application_Error?
*What is the difference between the inline and code behind?
*what is side by side execution?
*can we have two different versions of dot net frameworks running on the same
*What is CLR? Difference b/w CLR and JVM?
*What is CLI?
*What is CTS?
*What is .resx file meant for?
*Any idea of aspnet_regiis?
*Any idea of ASP NET State Service?
*Crystal report is only used for read only data and reporting purposes?
*We can add a crystal report in aspx page using two techniques, what are these?
*What is the difference between stroed procedure and stored function in SQL?
*Can we have an updateable view in SQL?
*What is connection pooling? how can we acheive that in
*What is DataSet?
*What is the difference between typed and untyped dataset?
*What is the difference bewteen accessing the data throgh the dataset and

1.Which controls do not have events?
Ans:Timer control.

2.What is the maximum size of the textbox?
3.Which property of the textbox cannot be changed at runtime?
Ans:Locked Porperty.
4.Which control cannot be placed in MDI?
Ans:The controls that do not have events.
5.Difference between a sub and a function.
Ands -A Sub Procedure is a method will not return a value
-A sub procedure will be defined with a “Sub” keyword
Sub ShowName(ByVal myName As String)
Console.WriteLine(”My name is: ” & myName)
End Sub

-A function is a method that will return value(s).
-A function will be defined with a “Function” keyword
Function FindSum(ByVal num1 As Integer, ByVal num2 As Integer) As Integer
Dim sum As Integer = num1 + num2
Return sum
End Function

6.Explain manifest & metadata.

Ands: Manifest is metadata about assemblies. Metadata is machine-readable
information about a resource, or “”data about data.” In .NET, metadata includes
type definitions, version information, external assembly references, and other
standardized information.

7.Difference between imperative and interrogative code
Ans. There are imperative and interrogative functions and I think they are talking
about that. Imperative functions are the one which return a
value while the interrogative functions do not return a value.

8.What are the two kinds of properties
Ans. Two types of properties in .Net: Get & Set
Two kind of properties are scalar properties and indexed properties

9.Explain constructor
Ans. Constructor is a method in the class which has the same name as the class (in
VB.Net its New()). It initialises the member attributes whenever an instance of the
class is created.

10.Describe ways of cleaning up objects
Ans. The run time will maintain a service called as garbage collector.
this service will take care of deallocating memory corresponding to works as a thread with least priority.when application
demenads for memory the runtime will take care of setting the high
priority for the garbage collector,so that it will be called for execution
and memory will be released.the programmer can make a call
to garbage colector by using GC class in system name space.

11. what are value types and reference types?
Ans. Value type - bool, byte, chat, decimal, double, enum , float, int, long, sbyte,
short, strut, uint, ulong, ushort
Value types are stored in the Stack
Reference type - class, delegate, interface, object, string
Reference types are stored in the Heap

12.How can you clean up objects holding resources from within the
Ands Call the dispose method from code for clean up of objects

13.Explain the life cycle of an ASP .NET page.
Life cycle of ASP.Net Web Form
Page Request >> Start >> Page Init >> Page Load >> Validation >>
PostBack Event Handling >> Page Rendering >> Page Unload
Page Request - When the page is requested ASP.Net determines
whether the page is to be parsed and compiled or a cached verion
of the page is to be sent without running the page.
Start - Page propertied REQUEST and RESPONSE are SET, if the
page is pastback request then the IsPostBack property is SET and
in addition to this UICulture property is also SET.
Page Initilization - In this the UniqueID of each property is SET.
If the request was postback the data is not yet loaded from the

Page Load - If it was a postback request then the data gets loaded
in the control from the ViewState and control property are set.
Validation - If any control validation present, they are performed
and IsValid property is SET for each control.
PostBack Event Handling - If it was a postback request then any
event handlers are called.
Page Rendering - Before this the viewstate is saved from the page
and RENDER method of each page is called.
Page Unload - Page is fully rendered and sent to the client(Browser)
and is discarded. Page property RESPONSE and REQUEST are unloaded.
14) .Net architecture?
The order starting from the bottom
1. CLR (Common Language Runtime)
2. .Net framework base classe
3. ASP.Net Web Form / Windows Form

15) What are object-oriented concepts?
Ans. Inheritance

16. How do you create multiple inheritance in c# and .NET?
Ans. Use interfaces
public class MyTest: IPaidInterface, ISoldInterface

17. When is web.config called?
Ans. Web.config is an xml configuration file. It is never directly called
unless we need to retrieve a configurations setting.

18. How many weg.configs can an application have?
Ans. One.

19. How do you set language in weg.config?
Ans. defaultLanguage=”vb”: This specifies the default code language.
debug=”true”: This specifies that the application should be run in debug

20. What does connection string consist of?
Ans. Server, user id, password, database name.

21. Where do you store connection string?
Ans. Web.config

22. What is abstract class?
Ans. An abstract class is a class that cannot be instantiated. Its purpose is
to act as a base class from which other classes may be derived.

23. What is difference between interface inheritance and class inheritance?
Ans. We can only inherit from one class but multiple interfaces. In addition, an
interface does not contain any implementation it just contains a series of signatures.
24. What are the collection classes?
Ans. Queue, Stack, BitArray, HashTable, LinkedList, ArrayList, Name
ValueCollection, Array, SortedList , HybridDictionary, ListDictionary, StringCollection,

25. What are the types of threading models?
Ans. Single Threading: This is the simplest and most common threading
model where a single thread corresponds to your entire application’s

Apartment Threading (STA): This allows multiple threads to exist in a
single application. In single threading apartment (STA), each thread
is isolated in it’s own apartment. The process may contain multiple
threads (apartments) however when an object is created in a
thread (i.e. apartment) it stays within that
apartment. If any communication needs to occur between different
threads (i.e. different apartments) then we must marshal the first
thread object to the second thread.
Free Threading: The most complex threading model. Unlike STA,
threads are not confined to their own apartments. Multiple treads can
make calls to the same methods and same components at the
same time.

26. What inheritance does VB.NET support?
Ans. Single inheritance using classes or multiple inheritance using

27. What is a runtime host?
Ans. The runtime host is the environment in which the CLR is started and

28. Describe the techniques for optimising your application?
Ans: Avoid round-trips to server. Perform validation on client.
. Save viewstate only when necessary.
. Employ caching.
. Leave buffering on unless there is a dire need to disable it.
. Use connection pooling.
. Use stored procedures instead of in-line SQL or dynamic SQL.

29. Differences between application and session
Ans. The session object maintains state on a per client basis whereas the
application object is on a per application basis and is consistent across
all client requests.

30. What is web application virtual directory?
Ans. A virtual directory appears to client browsers as though it were
contained in a Web server’s root directory, even though it can physically
Reside somewhere else.

31. What is isPostback property?
This property is used to check whether the page is being loaded and
accessed for the first time or whether the page is loaded in response
to the client postback.
Consider two combo boxes
In one lets have a list of countries
In the other, the states.
Upon selection of the first, the subsequent one should be populated in
accordance. So this requires postback property in combo boxes to be true.

32. Where do you store connection string?
Ans. Database connection string can be stored in the web config file.
The connection string can be stored in the WEB.Config file under
33. What does connection string consist of?
Ans. The connection string consists of the following parts:
In general:
Server: Whether local or remote.
Uid: User Id (sa-in sql server)
Password: The required password to be filled-in here
Database: The database name.

34. What are the collection classes?
Ans. The .NET Framework provides specialized classes for data storage
and retrieval.
These classes provide support for stacks, queues, lists, and hash tables.

35. What is isPostback property?
Ans. This property is used to check whether the page is being loaded and
accessed for the first time or whether the page is loaded in response
to the client postback.
Consider two combo boxes
In one lets have a list of countries
In the other, the states.
Upon selection of the first, the subsequent one should be populated in
accordance. So this requires postback property in combo boxes to be true.

36. What are Abstract base classes?
Ans. Abstact Class is nothing but a true virtual class..
This class cannot be instantiated instead it has to be inherited.
The method in abstract class are virtual and hence they can be overriden in
the child class.

37.What is difference between interface inhertance and class inheritance?
Ans. Interface inheritance: -
1. The accessibility modifier in Interface is public by defalut.
2. All the methods defined in the interface class should be oveririden in the child
Class Inheritance -
1. There is not restriction on the acessibility modifier in a class.
2. Only the method that are defined virtual should be overriden.

Ans. Application,Request,Responce,server and session

39. How do you get the value of a combo box in Javascript?
Ans. document.form_name.element_name.value

40. Why do we use Option Explicit?
Ans:- Correct answer is - This statement force the declaration of
variables in VB before using them.

41. How do you create a recordset object in VBScript?
//First of all declare a variable to hold the Recordset object,
ex-Dim objRs
//Now, Create this varible as a Recordset object, ex-
Set objRs=Server.CreateObject(ADODB.RECORDSET)

42. What is a class in CSS?
Ans. A class allows you to define different
style characteristics to the same HTML element.
class is a child to the id, id should be used only once, a css class
can be used multiple times:
div id=”banner”
p class=”alert”

43. When inserting strings into a SQL table in ASP what is the risk and
how can you prevent it?
Ans. SQL Injection, to prevent you probably need to use Stored Procedures
instead of inline/incode SQL

44. what is boxing?
what is unboxing?
what is deep copy & shallow copy?
Ans. Converting the value type into reverence type is call boxing.
Ans. Converting the reference type into value type is call unboxing.

When an object of value type is assigned with another, the data itself is
copied from one object to another. Suppose there are two integer

variables, count1 and count2. Further suppose that count1 contains the value 5 and
that count2 is assigned the value of count1.
count1 = 5;
count2 = count1;
Both count1 and count2 now contain their own copies of the data, in this case, the
value 5. They are independent. If count1 is now assigned the value 6, count2 will still
contain the value 5. This type of copy is referred to as a deep copy. The value itself is
If count1 is now assigned the value 6, count2 will still contain the value 5. This type
of copy is referred to as a deep copy.
For reference types copies work differently. Remember that a reference type
consists of two parts: the data on the heap and the address of the data stored in the
reference variable itself on the stack. When one reference variable is assigned to
another, the address stored in the first is copied to the second. They both then refer
to the same data content on the heap. This is referred to as a shallow copy.

45. What will be output for the given code?
Dim I as integer = 5
Response.Write (I & \” \”)
Loop Until I > 10
Ans. o/p: It generates error because of \” \”. (VB.NET)

46. What is the output for the following code snippet:
public class testClass
public static void Main(string[] args)
}//end Main
}//end class testClass

Basic .NET Framework

What is a IL?
Twist :- What is MSIL or CIL , What is JIT?
What is a CLR?
What is a CTS?
What is a CLS(Common Language Specification)?
What is a Managed Code?
What is a Assembly ?
What are different types of Assembly?
What is NameSpace?
What is Difference between NameSpace and Assembly?
If you want to view a Assembly how to you go about it ?
Twist : What is ILDASM ?
What is Manifest?
Where is version information stored of a assembly ?
Is versioning applicable to private assemblies?
What is GAC ?
Twist :- What are situations when you register .NET assembly in GAC ?
What is concept of strong names ?
Twist :- How do we generate strong names or what is the process of generating
names , What is use of SN.EXE , How do
we apply strong names to assembly ? , How do you sign an assembly ?
How to add and remove a assembly from GAC?
What is Delay signing ?

.NET Interview Questions

What is garbage collection?
Can we force garbage collector to run ?
What is reflection?
What are different type of JIT ?
What are Value types and Reference types ?
What is concept of Boxing and Unboxing ?
What’s difference between VB.NET and C# ?
What’s difference between System exceptions and Application exceptions?
What is CODE Access security?
What is a satellite assembly?
How to prevent my .NET DLL to be decompiled?
What’s the difference between Convert.toString and .toString() method ?
What is Native Image Generator (Ngen.exe)?
We have two version of the same assembly in GAC? I want my client to make choice
which assembly to choose?
What is CodeDom?

.NET Interoperability

How can we use COM Components in .NET?
Twist : What is RCW ?
Once i have developed the COM wrapper do i have to still register the COM in
How can we use .NET components in COM?
Twist :- What is CCW (COM callable wrapper) ?, What caution needs to be taken in
that .NET components is compatible with COM ?
How can we make Windows API calls in .NET?
When we use windows API in .NET is it managed or unmanaged code ?
What is COM ?
What is Reference counting in COM ?
Can you describe IUKNOWN interface in short ?
Can you explain what is DCOM ?
How do we create DCOM object in VB6?
How to implement DTC in .NET ?
How many types of Transactions are there in COM + .NET ?
How do you do object pooling in .NET ?
What are types of compatibility in VB6?
What is equivalent for regsvr32 exe in .NET ?


What is Multi-tasking ?
What is Multi-threading ?
What is a Thread ?
Did VB6 support multi-threading ?
Can we have multiple threads in one App domain ?
Which namespace has threading ?
Can you explain in brief how can we implement threading ?
How can we change priority and what the levels of priority are provided by .NET ?
What does Addressof operator do in background ?
How can you reference current thread of the method ?
What's Thread.Sleep() in threading ?
How can we make a thread sleep for infinite period ?
What is Suspend and Resume in Threading ?
What the way to stop a long running thread ?
How do i debug thread ?
What's Thread.Join() in threading ?
What are Daemon thread's and how can a thread be created as Daemon?
When working with shared data in threading how do you implement
synchronization ?
Can we use events with threading ?
How can we know a state of a thread?
What is a monitor object?
What are wait handles ?
Twist :- What is a mutex object ?
what is ManualResetEvent and AutoResetEvent ?
What is ReaderWriter Locks ?
How can you avoid deadlock in threading ?
What’s difference between thread and process?

Remoting and Webservices

What is a application domain?
What is .NET Remoting ?
Which class does the remote object has to inherit ?
What are two different types of remote object creation mode in .NET ?
Describe in detail Basic of SAO architecture of Remoting?
What are the situations you will use singleton architecture in remoting ?
What is fundamental of published or precreated objects in Remoting ?
What are the ways client can create object on server in CAO model ?
Are CAO stateful in nature ?
In CAO model when we want client objects to be created by “NEW” keyword is
any precautions to be taken ?
Is it a good design practice to distribute the implementation to Remoting Client ?
What is LeaseTime,SponsorshipTime ,RenewonCallTime and
Which config file has all the supported channels/protocol ?
How can you specify remoting parameters using Config files ?
Can Non-Default constructors be used with Single Call SAO?
Twist :- What are the limitation of constructors for Single call SAO ?
How can we call methods in remoting Asynchronously ?
What is Asynchronous One-Way Calls ?
What is marshalling and what are different kinds of marshalling ?
What is ObjRef object in remoting ?
What is a WebService ?
What is UDDI ?
What is DISCO ?
What is WSDL?
What the different phase/steps of acquiring a proxy object in Webservice ?
What is file extension of Webservices ?
Which attribute is used in order that the method can be used as WebService ?
What are the steps to create a webservice and consume it ?
Do webservice have state ?

Caching Concepts

What is application object ?
What’s the difference between Cache object and application object ?
How can get access to cache object ?
What are dependencies in cache and types of dependencies ?
Can you show a simple code showing file dependency in cache ?
What is Cache Callback in Cache ?
What is scavenging ?
What are different types of caching using cache object of ASP.NET?
How can you cache different version of same page using ASP.NET cache object ?
How will implement Page Fragment Caching ?
What are ASP.NET session and compare ASP.NET session with classic ASP session
Which various modes of storing ASP.NET session ?
Is Session_End event supported in all session modes ?
What are the precautions you will take in order that StateServer Mode work
properly ?
What are the precautions you will take in order that SQLSERVER Mode work
properly ?
Where do you specify session state mode in ASP.NET ?
What are the other ways you can maintain state ?
What are benefits and Limitation of using Hidden fields ?
What is ViewState ?
Do performance vary for viewstate according to User controls ?
What are benefits and Limitation of using Viewstate for state management?
How an you use Hidden frames to cache client data ?
What are benefits and Limitation of using Hidden frames?
What are benefits and Limitation of using Cookies?
What is Query String and What are benefits and Limitation of using Query Strings?
What is Object Oriented Programming ?
What’s a Class ?
What’s a Object ?
What’s the relation between Classes and Objects ?
What are different properties provided by Object-oriented systems ?
Twist :- Can you explain different properties of Object Oriented Systems?
Twist :- What’s difference between Association , Aggregation and Inheritance
How can we acheive inheritance in VB.NET ?
What are abstract classes ?
What’s a Interface ?
What is difference between abstract classes and interfaces?
What is a delegate ?
What are event’s ?
Do events have return type ?
Can event’s have access modifiers ?
Can we have shared events ?
What is shadowing ?
What’s difference between Shadowing and Overriding ?
What’s difference between delegate and events?
If we inherit a class do the private variables also get inherited ?
What are different accessibility levels defined in .NET ?
Can you prevent a class from overriding ?
What’s the use of “MustInherit” keyword in VB.NET ?
Why can not you specify accessibility modifier in Interface ?
What are similarities between Class and structure ?
What’s the difference between Class and structure’s ?
What does virtual keyword mean ?
What are shared (VB.NET)/Static(C#) variables?
What is Dispose method in .NET ?
Whats the use of “OverRides” and “Overridable” keywords ?
Where are all .NET Collection classes located ?
What is ArrayList ?
What’s a HashTable ?
Twist :- What’s difference between HashTable and ArrayList ?
What are queues and stacks ?
What is ENUM ?
What is nested Classes ?
What’s Operator Overloading in .NET?
In below sample code if we create a object of class2 which constructor will fire first
What’s the significance of Finalize method in .NET?
Why is it preferred to not use finalize for clean up?
How can we suppress a finalize method?
What’s the use of DISPOSE method?
How do I force the Dispose method to be called automatically, as clients can forget
to call
Dispose method?
In what instances you will declare a constructor to be private?
Can we have different access modifiers on get/set methods of a property ?
If we write a goto or a return statement in try and catch block will the finally block
execute ?
What is Indexer ?
Can we have static indexer in C# ?
In a program there are multiple catch blocks so can it happen that two catch blocks
executed ?
What is the difference between System.String and System.StringBuilder classes?


What’s the sequence in which ASP.NET events are processed ?
In which event are the controls fully loaded ?
How can we identify that the Page is PostBack ?
How does ASP.NET maintain state in between subsequent request ?
What is event bubbling ?
How do we assign page specific attributes ?
Administrator wants to make a security check that no one has tampered with
, how can he ensure this ? 153
What’s the use of @ Register directives ?
What’s the use of SmartNavigation property ?
What is AppSetting Section in “Web.Config” file ?
Where is ViewState information stored ?
What’s the use of @ OutputCache directive in ASP.NET?
How can we create custom controls in ASP.NET ?
How many types of validation controls are provided by ASP.NET ?
Can you explain what is “AutoPostBack” feature in ASP.NET ?
How can you enable automatic paging in DataGrid ?
What’s the use of “GLOBAL.ASAX” file ?
What’s the difference between “Web.config” and “Machine.Config” ?
What’s a SESSION and APPLICATION object ?
What’s difference between Server.Transfer and response.Redirect ?
What’s difference between Authentication and authorization?
What is impersonation in ASP.NET ?
Can you explain in brief how the ASP.NET authentication process works?
What are the various ways of authentication techniques in ASP.NET?
How does authorization work in ASP.NET?
What’s difference between Datagrid , Datalist and repeater ?
From performance point of view how do they rate ?
What’s the method to customize columns in DataGrid?
How can we format data inside DataGrid?
How will decide the design consideration to take a Datagrid , datalist or repeater ?
Difference between ASP and ASP.NET?
What are major events in GLOBAL.ASAX file ?
What order they are triggered ?
Do session use cookies ?
How can we force all the validation control to run ?
How can we check if all the validation control are valid and proper ?
If you have client side validation is enabled in your Web page , Does that mean
side code is not run?
Which JavaScript file is referenced for validating the validators at the client side ?
How to disable client side script in validators?
I want to show the entire validation error message in a message box on the client
You find that one of your validation is very complicated and does not fit in any of
validators , so what will you do ?
What is Tracing in ASP.NET ?
How do we enable tracing ?
What exactly happens when ASPX page is requested from Browser?
How can we kill a user session ?
How do you upload a file in ASP.NET ?
How do I send email message from ASP.NET ?
What are different IIS isolation levels?
ASP used STA threading model , whats the threading model used for ASP.NET ?
Whats the use of <%@ page aspcompat=true %> attribute ?
Explain the differences between Server-side and Client-side code?
Can you explain Forms authentication in detail ?
How do I sign out in forms authentication ?
If cookies are not enabled at browser end does form Authentication work?
How to use a checkbox in a datagrid?
What are the steps to create a windows service in VB.NET ?
What’s the difference between “Web farms” and “Web garden”?
How do we configure “WebGarden”?
What is the main difference between Gridlayout and FlowLayout ?

.NET Architecture

What are design patterns ?
What’s difference between Factory and Abstract Factory Pattern’s?
What’s MVC pattern?
Twist: - How can you implement MVC pattern in ASP.NET?
How can we implement singleton pattern in .NET?
How do you implement prototype pattern in .NET?
Twist: - How to implement cloning in .NET ? , What is shallow copy and deep copy ?
What are the situations you will use a Web Service and Remoting in projects?
Can you give a practical implementation of FAÇADE patterns?
How can we implement observer pattern in .NET?
What is three tier architecture?
Have you ever worked with Microsoft Application Blocks, if yes then which?
What is Service Oriented architecture?
What are different ways you can pass data between tiers?
What is Windows DNA architecture?
What is aspect oriented programming?


What is the namespace in which .NET has the data functionality classes ?
Can you give a overview of ADO.NET architecture ?
What are the two fundamental objects in ADO.NET ?
What is difference between dataset and datareader ?
What are major difference between classic ADO and ADO.NET ?
What is the use of connection object ?
What is the use of command objects and what are the methods provided by the
object ?
What is the use of dataadapter ?
What are basic methods of Dataadapter ?
What is Dataset object?
What are the various objects in Dataset ?
How can we connect to Microsoft Access , Foxpro , Oracle etc ?
How do we connect to SQL SERVER , which namespace do we use ?
How do we use stored procedure in ADO.NET and how do we provide parameters to
the stored procedures?
How can we force the connection object to close after my datareader is closed ?
I want to force the datareader to return only schema of the datastore rather than
data ?
How can we fine tune the command object when we are expecting a single row or a
value ?
Which is the best place to store connectionstring in .NET projects ?
What are steps involved to fill a dataset ?
Twist :- How can we use dataadapter to fill a dataset ?
What are the various methods provided by the dataset object to generate XML?
How can we save all data from dataset ?
How can we check that some changes have been made to dataset since it was
loaded ?
Twist :- How can we cancel all changes done in dataset ? , How do we get values
are changed in a dataset ?
How can we add/remove row’s in “DataTable” object of “DataSet” ?
What’s basic use of “DataView” ?
What’s difference between “DataSet” and “DataReader” ?
Twist :- Why is DataSet slower than DataReader ?
How can we load multiple tables in a DataSet ?
How can we add relation’s between table in a DataSet ?
What’s the use of CommandBuilder ?
What’s difference between “Optimistic” and “Pessimistic” locking ?
How many way’s are there to implement locking in ADO.NET ?
How can we perform transactions in .NET?
What’s difference between Dataset. clone and Dataset. copy ?
Can you explain the difference between an ADO.NET Dataset and an ADO
Explain in detail the fundamental of connection pooling?
What is Maximum Pool Size in ADO.NET Connection String?
How to enable and disable connection pooling?

A Microsoft.NET application can be run only after the MSIL code is translated into
native machine code. In .NET Framework,
the intermediate language is complied "just in time" (JIT) into native code when the
application or component is run instead of
compiling the application at development time. The Microsoft.NET runtime consists
of two JIT compilers. They are standard JIT
compiler and the EconoJIT compiler. The EconoJIT compiler compiles faster than the
standard JIT compiler, but the code it produces is not
as optimized as the code obtained from the standard JIT compiler.

.Net Framework 2.0 Advantages:-

The .Net Framework (version 2.0) includes 51 assemblies.

The .Net Framework (version 2.0) includes 18,619 types; 12,909 classes; 401,759
public methods; 93,105 public properties and 30,546 public events.

It includes a new feature called Control State. Control state is similar to view state
except that is used to preserve only critical information. For example the gridview
control uses control state to store the selected row. Even if you disable the
viewstate, the gridview control remembers which row is selected.

We can precompile an entire ASP.Net application by using the aspnet_compiler.exe
command line tool. If you precompile an application, users do not experience the
compilation delay resulting from the first page request.

Dynamic Compilation in detail:-

The entire contents of an ASP.NET page, including all script and HTML content, are
compiled into a .net class. If we request a page that does not exist ASP.NET
automatically compiles the page into a new class and stores the compiled class (the
assembly) in the temporary ASP.NET files folder located in the following path

\Windows\Microsoft.NET\Framework\[version]\Temporary ASP.Net files

The next time when anyone request for the same page the page is not compiled
again the previous one is executed even if you request the page after three years.

When the class is added to the Temporary ASP.NET files folder, a file dependency
created between the class and the original ASP.NET page. If the ASP.NET page is
modified in any way, the corresponding .net class is automatically deleted. The next
time when someone request the page, the Framework automatically compiles the
modified page source into a new .net class. This process is called Dynamic
compilation. Dynamic compilation enables ASP.Net application o support thousands
of simultaneous users.

We can disable dynamic compilation for a single page, the pages in folder, or an
entire website with the CompilationMode attribute.

Disabling the compilation is useful when thousands of pages in a website and you do
not want to load an assembly into memory for every page. When the compilation
attribute is said to the value Never, the page is never compiled and an assembly is
never generated for the page. The page is interpreted at runtime. We cannot
disable the compilation code that includes server side code.

Literal Control:-

We can use literal control to display text or HTML content in a browser. It does not
render its content inside a <span> tag.
It does not support CSS class or Back color properties. However it supports the
mode property that is not supported by the label control.

Using Client Scripts with Button Controls:-

<asp: Button id = “btnDelete” Text=”Delete” onclick=”btnDelete_Click”
onclientclick=”return confirm (‘Are you sure?’);” runat =”server”/>

<asp: Button id = “btnSubmit” Text = “Submit” onmouseover=”this.value=’click
here!’” onmouseout=”this.value=’Submit’” runat=”server”/>

Mater Pages:-

You can nest content place holder controls in a master page. If you do this, then you
have the option of overriding greater or smaller areas of content in master page.

You cannot work with nested master pages in visual web developer while in design
view. If you need to nest master pages, then you need to stick to source view.

Relative URLs used by ASP.NET controls in master page are automatically
reinterpreted relative to master page. This process of reinterpretation is called
rebasing. Only ASP.NET control properties decorated with URL property attribute
are rebased.
You will receive null reference exception if you use the Page.Header property when
the master page does not contain a server-side <head> tag.


The contents of a theme folder are automatically compiled in the background into a
new class. So you want to be careful not to name a theme with a class name that
conflicts with an existing class name in your project.

The textbox control includes a Runat=”server” attribute, but it does not include an
ID attribute. You must always include a Runat attribute, but you can never include
the ID attribute when declaring a control in a skin.

We can not create a skin that applies to the properties of a user control. However,
you can skin the controls contained in a user control.

AJAX and User Controls:-

AJAX (Asynchronous JavaScript and XML) enables you to update content in a page
without posting back to the server. In the ASP.NET Framework, AJAX is referred to
as ‘client callbacks’. To add AJAX support to a user control, you must implement the
ICallBackEventHandler interface and add the necessary JavaScript scripts to process
the results of the AJAX call.

Steps for implementing AJAX:-

? Create a client script for invoking the AJAX call. You can get this script with the
Page.ClientScript.GetCallbackEventReference () method.

? Create a sever methods named RaiseCallbackEvent() and GetCallbackResult(),
which returns a string value from the server.

? Create a client method that receives the value from the server
RaiseCallbackEvent() method and does something with the value.

what is the difference .netframework 1.1 and2.0
what are the features in it

1. What are the main differences between asp and

    ASP 3.0
• Supports VBScript and JavaScript
o scripting languages are limited in scope
o interpreted from top to bottom each time the page is loaded
• Files end with *.asp extension
• 5 objects: Request, Response, Server, Application, Session
• Queried databases return recordsets
• Uses conventional HTML forms for data collection


• Supports a number of languages including Visual Basic, C#, and JScript
o code is compiled into .NET classes and stored to speed up multiple hits on a
o object oriented and event driven makes coding web pages more like
traditional applications
• Files end with *.aspx extension
• .NET contains over 3400 classes
• XML-friendly data sets are used instead of recordsets
• Uses web forms that look like HTML forms to the client, but add much
functionality due to server-side coding
• Has built-in validation objects
• Improved debugging feature (great news for programmers)
• ASP .NET controls can be binded to a data source, including XML recordsets

2. What is a user control?

• An ASP.NET user control is a group of one or more server controls or static
HTML elements that encapsulate a piece of functionality. A user control could
simply be an extension of the functionality of an existing server control(s) (such
as an image control that can be rotated or a calendar control that stores the
date in a text box). Or, it could consist of several elements that work and
interact together to get a job done (such as several controls grouped together
that gather information about a user's previous work experience).

3. What are different types of controls available in
• HTML server controls HTML elements exposed to the server so you can
program them. HTML server controls expose an object model that maps very
closely to the HTML elements that they render.
• Web server controls Controls with more built-in features than HTML server
controls. Web server controls include not only form-type controls such as
buttons and text boxes, but also special-purpose controls such as a calendar.
Web server controls are more abstract than HTML server controls in that their
object model does not necessarily reflect HTML syntax.
• Validation controls Controls that incorporate logic to allow you to test a user's
input. You attach a validation control to an input control to test what the user
enters for that input control. Validation controls are provided to allow you to
check for a required field, to test against a specific value or pattern of
characters, to verify that a value lies within a range, and so on.
• User controls Controls that you create as Web Forms pages. You can embed
Web Forms user controls in other Web Forms pages, which is an easy way to
create menus, toolbars, and other reusable elements.
• Note You can also create output for mobile devices. To do so, you use the
same ASP.NET page framework, but you create Mobile Web Forms instead of
Web Forms pages and use controls specifically designed for mobile devices.
Source: MSDN

4. What are the validation controls available in

Type of validation Control to use

Required entry RequiredFieldValidator Ensures that the user does not skip an
Comparison to a value CompareValidator Compares a user's entry against a
constant value, or against a property value of another control, using a
comparison operator (less than, equal, greater than, and so on).
Range checking RangeValidator Checks that a user's entry is between specified
lower and upper boundaries. You can check ranges within pairs of numbers,
alphabetic characters, and dates.
Pattern matching RegularExpressionValidator Checks that the entry matches a
pattern defined by a regular expression. This type of validation allows you to
check for predictable sequences of characters, such as those in social security
numbers, e-mail addresses, telephone numbers, postal codes, and so on.
User-defined CustomValidator Checks the user's entry using validation logic that
you write yourself. This type of validation allows you to check for values derived
at run time.
Source: MSDN

5. How will you upload a file to IIS in Asp and how will you do the same in
First of all, we need a HTML server control to allow the user to select the file.
This is nothing but the same old <input tag, with the type set to File, such as
<input type=file id=”myFile” runat=server />. This will give you the textbox and a
browse button. Once you have this, the user can select any file from their
computer (or even from a network). Then, in the Server side, we need the
following line to save the file to the Web Server.

myFile.PostedFile.SaveAs ("DestinationPath")

Note: The Form should have the following ENC Type
<form enctype="multipart/form-data" runat="server">

Source: ASP Alliance
6. What is Attribute Programming? What are attributes? Where are they used?

Attributes are a mechanism for adding metadata, such as compiler instructions
and other data about your data, methods, and classes, to the program itself.
Attributes are inserted into the metadata and are visible through ILDasm and
other metadata-reading tools. Attributes can be used to identify or use the data
at runtime execution using .NET Reflection.

7. What is the difference between Data Reader & Dataset?

Data Reader is connected, read only forward only record set.
Dataset is in memory database that can store multiple tables, relations and
constraints; moreover dataset is disconnected and is not aware of the data

8. What is the difference between server side and client side code?

Server code is executed on the web server where as the client code is executed
on the browser machine.

9. Why would you use “EnableViewState” property? What are the

EnableViewState allows me to retain the values of the controls properties across
the requests in the same session. It hampers the performance of the
10. What is the difference between Server. Transfer and Response. Redirect?

The Transfer method allows you to transfer from inside one ASP page to
another ASP page. All of the state information that has been created for the first
(calling) ASP page will be transferred to the second (called) ASP page. This
transferred information includes all objects and variables that have been given a
value in an Application or Session scope, and all items in the Request
collections. For example, the second ASP page will have the same SessionID as
the first ASP page.

When the second (called) ASP page completes its tasks, you do not return to the
first (calling) ASP page. All these happen on the server side browser is not aware
of this.
The redirect message issue HTTP 304 to the browser and causes browser to got
the specified page. Hence there is round trip between client and server. Unlike
transfer, redirect doesn’t pass context information to the called page.

11. What is the difference between Application_start and Session_start?

Application_start gets fired when an application receive the very first request.
Session_start gets fired for each of the user session.

12. What is inheritance and when would you use inheritance?

The concept of child class inheriting the behavior of the parent is called
If there are many classes in an application that have some part of their behavior
common among all , inheritance would be used.

13. What is the order of events in a web form?

1. Init
2. Load
3. Cached post back events
4. Prerender
5. Unload

14. Can you edit Data in repeater control?

15. Which template you must provide to display data in a repeater control?

Item Template

16. How can you provide an alternating color scheme in a Data Grid?

Use ALTERNATINGITEMSTYLE and ITEMSTYLE, attributes or Templates

17. Is it possible to bind a data to Textbox?


18. What method I should call to bind data to control?

Bind Data ()

19. How can I kill a user session?

Call session. abandon.

21. Which is the common property among all the validation controls?


22. How do you bind a data grid column manually?

Use BoundColumn tag.

23. Web services can only be written in .NET, true or false?


24. What does WSDL, UDDI stands for?

Web Service Description Language.
Universal Description Discovery and Integration
25. How can you make a property read only? (C#)

Use key word Read Only

25. Which validation control is used to match values in two controls?
Compare Validation control.

26. To test a Web Service I must create either web application or windows
application. True or false?


27. How many classes can a single .NET assembly contains?

Any number

28. What are the data types available in JavaScript?

Object is the only data type available.

29. Is it possible to share session information among ASP and ASPX page?

No, it is not possible as both of these are running under different processes.

30. What are the caching techniques available?
Page cahahing.
Fragment Caching
And Data Caching

31. What are the different types of authentication modes available?

1. Window.
2. Form.
3. Passport.
4. None.

32. Explain the steps involved to populate dataset with data?

Open connection
Initialize Adapter passing SQL and connection as parameter
Initialize Dataset
Call Fill method of the adapter passes dataset as the parameter
Close connection.
33. Can I have data from two different sources into a single dataset?

Yes, it is possible.

34. Is it possible load XML into a Data Reader?


35. Is it possible to have tables in the dataset that are not bound to any data

Yes, we can create table object in code and add it to the dataset.

36. Why do you deploy an assembly into GAC?

To allow other application to access the shared assembly.

37. How do you uninstall assembly from GAC?

Use Gacutil.exe with U switch.

38. What does Regasm do?

The Assembly Registration tool reads the metadata within an assembly and adds
the necessary entries to the registry, which allows COM clients to create .NET
Framework classes transparently. Once a class is registered, any COM client can
use it as though the class were a COM class. The class is registered only once,
when the assembly is installed. Instances of classes within the assembly cannot
be created from COM until they are actually registered.

39. What is the difference between Execute Scalar and ExceuteNoneQuery?

Execute Scalar returns the value in the first row first column of a query result
ExceuteNonQuery return number of rows affected.

40. What is an assembly?

Assembly is a deployment unit of .NET application. In practical terms assembly is
an Executable or a class library.

41. What is CLR?
The common language runtime is the execution engine for .NET Framework
It provides a number of services, including the following:
• Code management (loading and execution)
Application memory isolation
• Verification of type safety
• Conversion of IL to native code
• Access to metadata (enhanced type information)
• Managing memory for managed objects
• Enforcement of code access security
• Exception handling, including cross-language exceptions
• Interoperation between managed code, COM objects, and pre-existing DLLs
(unmanaged code and data)
• Automation of object layout
• Support for developer services (profiling, debugging, and so on)

42. What is the common type system (CTS)?

The common type system is a rich type system, built into the common language
runtime that supports the types and operations found in most programming
languages. The common type system supports the complete implementation of
a wide range of programming languages.

43. What is the Common Language Specification (CLS)?

The Common Language Specification is a set of constructs and constraints that
serves as a guide for library writers and compiler writers. It allows libraries to be
fully usable from any language supporting the CLS, and for those languages to
integrate with each other. The Common Language Specification is a subset of
the common type system. The Common Language Specification is also
important to application developers who are writing code that will be used by
other developers. When developers design publicly accessible APIs following the
rules of the CLS, those APIs are easily used from all other programming
languages that target the common language runtime.

44. What is the Microsoft Intermediate Language (MSIL)?

MSIL is the CPU-independent instruction set into which .NET Framework
programs are compiled. It contains instructions for loading, storing, initializing,
and calling methods on objects.
Combined with metadata and the common type system, MSIL allows for true
cross-language integration.
Prior to execution, MSIL is converted to machine code. It is not interpreted.

45. What is managed code and managed data?

Managed code is code that is written to target the services of the common
language runtime (see what is the Common Language Runtime?). In order to
target these services, the code must provide a minimum level of information
(metadata) to the runtime. All C#, Visual Basic .NET, and JScript .NET code is
managed by default. Visual Studio .NET C++ code is not managed by default, but
the compiler can produce managed code by specifying a command-line switch
Closely related to managed code is managed data—data that is allocated and
de-allocated by the common language runtime's garbage collector. C#, Visual
Basic, and JScript .NET data is managed by default. C# data can, however, be
marked as unmanaged through the use of special keywords. Visual Studio .NET
C++ data is unmanaged by default (even when using the /CLR switch), but when
using Managed Extensions for C++, a class can be marked as managed by using
the __gc keyword. As the name suggests, this means that the memory for
instances of the class is managed by the garbage collector. In addition, the class
becomes a full participating member of the .NET Framework community, with
the benefits and restrictions that brings. An example of a benefit is proper
interoperability with classes written in other languages (for example, a managed
C++ class can inherit from a Visual Basic class). An example of a restriction is
that a managed class can only inherit from one base class.

46. What is an assembly?

An assembly is the primary building block of a .NET Framework application. It is
a collection of functionality that is built, versioned, and deployed as a single
implementation unit (as one or more files). All managed types and resources are
marked either as accessible only within their implementation unit or as
accessible by code outside that unit.

Assemblies are self-describing by means of their manifest, which is an integral
part of every assembly.

The manifest: Establishes the assembly identity (in the form of a text name),
version, culture, and digital signature (if the assembly is to be shared across
Defines what files (by name and file hash) make up the assembly
Specifies the types and resources that make up the assembly, including which
are exported from the assembly.
Itemizes the compile-time dependencies on other assemblies.
Specifies the set of permissions required for the assembly to run properly.

This information is used at run time to resolve references, enforce version
binding policy, and validate the integrity of loaded assemblies. The runtime can
determine and locate the assembly for any running object, since every type is
loaded in the context of an assembly. Assemblies are also the unit at which code
access security permissions are applied. The identity evidence for each assembly
is considered separately when determining what permissions to grant the code
it contains.
The self-describing nature of assemblies also helps makes zero-impact install
and XCOPY deployment feasible.

47. What are private assemblies and shared assemblies?

A private assembly is used only by a single application, and is stored in that
application's install directory (or a subdirectory therein). A shared assembly is
one that can be referenced by more than one application. In order to share an
assembly, the assembly must be explicitly built for this purpose by giving it a
cryptographically strong name (referred to as a strong name). By contrast, a
private assembly name need only be unique within the application that uses it.
By making a distinction between private and shared assemblies, we introduce
the notion of sharing as an explicit decision. Simply by deploying private
assemblies to an application directory, you can guarantee that that application
will run only with the bits it was built and deployed with. References to private
assemblies will only be resolved locally to the private application directory.
There are several reasons you may elect to build and use shared assemblies,
such as the ability to express version policy. The fact that shared assemblies
have a cryptographically strong name means that only the author of the
assembly has the key to produce a new version of that assembly. Thus, if you
make a policy statement that says you want to accept a new version of an
assembly, you can have some confidence that version updates will be controlled
and verified by the author. Otherwise, you don't have to accept them.
For locally installed applications, a shared assembly is typically explicitly
installed into the global assembly cache (a local cache of assemblies maintained
by the .NET Framework). Key to the version management features of the .NET
Framework is that downloaded code does not affect the execution of locally
installed applications. Downloaded code is put in a special download cache and
is not globally available on the machine even if some of the downloaded
components are built as shared assemblies.
The classes that ship with the .NET Framework are all built as shared assemblies.

48. If I want to build a shared assembly, does that require the overhead of
signing and managing key pairs?

Building a shared assembly does involve working with cryptographic keys. Only
the public key is strictly needed when the assembly is being built. Compilers
targeting the .NET Framework provide command line options (or use custom
attributes) for supplying the public key when building the assembly. It is
common to keep a copy of a common public key in a source database and point
build scripts to this key. Before the assembly is shipped, the assembly must be
fully signed with the corresponding private key. This is done using an SDK tool
called SN.exe (Strong Name).
Strong name signing does not involve certificates like Authenticode does. There
are no third party organizations involved, no fees to pay, and no certificate
chains. In addition, the overhead for verifying a strong name is much less than it
is for Authenticode. However, strong names do not make any statements about
trusting a particular publisher. Strong names allow you to ensure that the
contents of a given assembly haven't been tampered with, and that the
assembly loaded on your behalf at run time comes from the same publisher as
the one you developed against. But it makes no statement about whether you
can trust the identity of that publisher.

49. What is the difference between a namespace and an assembly name?

A namespace is a logical naming scheme for types in which a simple type name,
such as MyType, is preceded with a dot-separated hierarchical name. Such a
naming scheme is completely under the control of the developer. For example,
types MyCompany.FileAccess.A and MyCompany.FileAccess.B might be logically
expected to have functionality related to file access. The .NET Framework uses a
hierarchical naming scheme for grouping types into logical categories of related
functionality, such as the Microsoft® ASP.NET application framework, or
remoting functionality. Design tools can make use of namespaces to make it
easier for developers to browse and reference types in their code. The concept
of a namespace is not related to that of an assembly. A single assembly may
contain types whose hierarchical names have different namespace roots, and a
logical namespace root may span multiple assemblies. In the .NET Framework, a
namespace is a logical design-time naming convenience, whereas an assembly
establishes the name scope for types at run time.
50. What options are available to deploy my .NET applications?

The .NET Framework simplifies deployment by making zero-impact install and
XCOPY deployment of applications feasible. Because all requests are resolved
first to the private application directory, simply copying an application's
directory files to disk is all that is needed to run the application. No registration
is required.
This scenario is particularly compelling for Web applications, Web Services, and
self-contained desktop applications. However, there are scenarios where XCOPY
is not sufficient as a distribution mechanism. An example is when the
application has little private code and relies on the availability of shared
assemblies, or when the application is not locally installed (but rather
downloaded on demand). For these cases, the .NET Framework provides
extensive code download services and integration with the Windows Installer.
The code download support provided by the .NET Framework offers several
advantages over current platforms, including incremental download, code
access security (no more Authenticode dialogs), and application isolation (code
downloaded on behalf of one application doesn't affect other applications). The
Windows Installer is another powerful deployment mechanism available to .NET
applications. All of the features of Windows Installer, including publishing,
advertisement, and application repair will be available to .NET applications in
Windows Installer 2.0.

51. I've written an assembly that I want to use in more than one application.
Where do I deploy it?

Assemblies that are to be used by multiple applications (for example, shared
assemblies) are deployed to the global assembly cache. In the prerelease and
Beta builds, use the /i option to the GACUtil SDK tool to install an assembly into
the cache:
gacutil /i myDll.dll
Windows Installer 2.0, which ships with Windows XP and Visual Studio .NET will
be able to install assemblies into the global assembly cache.

52. How can I see what assemblies are installed in the global assembly cache?

The .NET Framework ships with a Windows shell extension for viewing the
assembly cache. Navigating to % windir%\assembly with the Windows Explorer
activates the viewer.

53. What is an application domain?
An application domain (often AppDomain) is a virtual process that serves to
isolate an application. All objects created within the same application scope (in
other words, anywhere along the sequence of object activations beginning with
the application entry point) are created within the same application domain.
Multiple application domains can exist in a single operating system process,
making them a lightweight means of application isolation.

An OS process provides isolation by having a distinct memory address space.
While this is effective, it is also expensive, and does not scale to the numbers
required for large web servers. The Common Language Runtime, on the other
hand, enforces application isolation by managing the memory use of code
running within the application domain. This ensures that it does not access
memory outside the boundaries of the domain. It is important to note that only
type-safe code can be managed in this way (the runtime cannot guarantee
isolation when unsafe code is loaded in an application domain).

54. What is garbage collection?

Garbage collection is a mechanism that allows the computer to detect when an
object can no longer be accessed. It then automatically releases the memory
used by that object (as well as calling a clean-up routine, called a "finalizer,"
which is written by the user). Some garbage collectors, like the one used by
.NET, compact memory and therefore decrease your program's working set.

55. How does non-deterministic garbage collection affect my code?

For most programmers, having a garbage collector (and using garbage collected
objects) means that you never have to worry about deallocating memory, or
reference counting objects, even if you use sophisticated data structures. It
does require some changes in coding style, however, if you typically deallocate
system resources (file handles, locks, and so forth) in the same block of code
that releases the memory for an object. With a garbage collected object you
should provide a method that releases the system resources deterministically
(that is, under your program control) and let the garbage collector release the
memory when it compacts the working set.

56. Can I avoid using the garbage collected heap?

All languages that target the runtime allow you to allocate class objects from
the garbage-collected heap. This brings benefits in terms of fast allocation, and
avoids the need for programmers to work out when they should explicitly 'free'
each object.
The CLR also provides what are called ValueTypes—these are like classes, except
that ValueType objects are allocated on the runtime stack (rather than the
heap), and therefore reclaimed automatically when your code exits the
procedure in which they are defined. This is how "structs" in C# operate.
Managed Extensions to C++ lets you choose where class objects are allocated. If
declared as managed Classes, with the __gc keyword, then they are allocated
from the garbage-collected heap. If they don't include the __gc keyword, they
behave like regular C++ objects, allocated from the C++ heap, and freed
explicitly with the "free" method.

57. How do in-process and cross-process communication work in the Common
Language Runtime?

There are two aspects to in-process communication: between contexts within a
single application domain, or across application domains. Between contexts in
the same application domain, proxies are used as an interception mechanism.
No marshaling/serialization is involved. When crossing application domains, we
do marshaling/serialization using the runtime binary protocol.
Cross-process communication uses a pluggable channel and formatter protocol,
each suited to a specific purpose.
If the developer specifies an endpoint using the tool soapsuds.exe to generate a
metadata proxy, HTTP channel with SOAP formatter is the default.
If a developer is doing explicit remoting in the managed world, it is necessary to
be explicit about what channel and formatter to use. This may be expressed
administratively, through configuration files, or with API calls to load specific
channels. Options are:
HTTP channel w/ SOAP formatter (HTTP works well on the Internet, or anytime
traffic must travel through firewalls)
TCP channel w/ binary formatter (TCP is a higher performance option for local-
area networks (LANs))
When making transitions between managed and unmanaged code, the COM
infrastructure (specifically, DCOM) is used for remoting. In interim releases of
the CLR, this applies also to serviced components (components that use COM+
services). Upon final release, it should be possible to configure any remotable
Distributed garbage collection of objects is managed by a system called "leased
based lifetime." Each object has a lease time, and when that time expires, the
object is disconnected from the remoting infrastructure of the CLR. Objects
have a default renew time-the lease is renewed when a successful call is made
from the client to the object. The client can also explicitly renew the lease.

58. Can I use COM objects from a .NET Framework program?
Yes. Any COM component you have deployed today can be used from managed
code, and in common cases the adaptation is totally automatic.
Specifically, COM components are accessed from the .NET Framework by use of
a runtime callable wrapper (RCW). This wrapper turns the COM interfaces
exposed by the COM component into .NET Framework-compatible interfaces.
For OLE automation interfaces, the RCW can be generated automatically from a
type library. For non-OLE automation interfaces, a developer may write a
custom RCW and manually map the types exposed by the COM interface to .NET
Framework-compatible types.

59. Can .NET Framework components be used from a COM program?

Yes. Managed types you build today can be made accessible from COM, and in
the common case the configuration is totally automatic. There are certain new
features of the managed development environment that are not accessible
from COM. For example, static methods and parameterized constructors cannot
be used from COM. In general, it is a good idea to decide in advance who the
intended user of a given type will be. If the type is to be used from COM, you
may be restricted to using those features that are COM accessible.
Depending on the language used to write the managed type, it may or may not
be visible by default.
Specifically, .NET Framework components are accessed from COM by using a
COM callable wrapper (CCW). This is similar to an RCW (see previous question),
but works in the opposite direction. Again, if the .NET Framework development
tools cannot automatically generate the wrapper, or if the automatic behavior is
not what you want, a custom CCW can be developed.

60. Can I use the Win32 API from a .NET Framework program?

Yes. Using platform invoke, .NET Framework programs can access native code
libraries by means of static DLL entry points.
Here is an example of C# calling the Win32 MessageBox function:
using System;
using System.Runtime.InteropServices;

class MainApp
[DllImport("user32.dll", EntryPoint="MessageBox")]
public static extern int MessageBox(int hWnd, String strMessage, String
strCaption, uint uiType);

public static void Main()
MessageBox( 0, "Hello, this is PInvoke in operation!", ".NET", 0 );

61. What do I have to do to make my code work with the security system?

Usually, not a thing—most applications will run safely and will not be
exploitable by malicious attacks. By simply using the standard class libraries to
access resources (like files) or perform protected operations (such as a
reflection on private members of a type), security will be enforced by these
libraries. The one simple thing application developers may want to do is include
a permission request (a form of declarative security) to limit the permissions
their code may receive (to only those it requires). This also ensures that if the
code is allowed to run, it will do so with all the permissions it needs.
Only developers writing new base class libraries that expose new kinds of
resources need to work directly with the security system. Instead of all code
being a potential security risk, code access security constrains this to a very
small bit of code that explicitly overrides the security system.

62. Why does my code get a security exception when I run it from a network
shared drive?

Default security policy gives only a restricted set of permissions to code that
comes from the local intranet zone. This zone is defined by the Internet Explorer
security settings, and should be configured to match the local network within an
enterprise. Since files named by UNC or by a mapped drive (such as with the
NET USE command) are being sent over this local network, they too are in the
local intranet zone.
The default is set for the worst case of an unsecured intranet. If your intranet is
more secure you can modify security policy (with the .NET Framework
Configuration tool or the CASPol tool) to grant more permissions to the local
intranet, or to portions of it (such as specific machine share names).

63. How do I make it so that code runs when the security system is stopping it?

Security exceptions occur when code attempts to perform actions for which it
has not been granted permission. Permissions are granted based on what is
known about code; especially its location. For example, code run from the
Internet is given fewer permissions than that run from the local machine
because experience has proven that it is generally less reliable. So, to allow code
to run that is failing due to security exceptions, you must increase the
permissions granted to it. One simple way to do so is to move the code to a
more trusted location (such as the local file system). But this won't work in all
cases (web applications are a good example, and intranet applications on a
corporate network are another). So, instead of changing the code's location, you
can also change security policy to grant more permissions to that location. This
is done using either the .NET Framework Configuration tool or the code access
security policy utility (caspol.exe). If you are the code's developer or publisher,
you may also digitally sign it and then modify security policy to grant more
permissions to code bearing that signature. When taking any of these actions,
however, remember that code is given fewer permissions because it is not from
an identifiably trustworthy source—before you move code to your local
machine or change security policy, you should be sure that you trust the code to
not perform malicious or damaging actions.

64. How do I administer security for my machine? For an enterprise?

The .NET Framework includes the .NET Framework Configuration tool, an MMC
snap-in (mscorcfg.msc), to configure several aspects of the CLR including
security policy. The snap-in not only supports administering security policy on
the local machine, but also creates enterprise policy deployment packages
compatible with System Management Server and Group Policy. A command line
utility, CASPol.exe, can also be used to script policy changes on the computer. In
order to run either tool, in a command prompt, change the current directory to
the installation directory of the .NET Framework (located in
%windir%\Microsoft.Net\Framework\v1.0.2914.16\) and type mscorcfg.msc or

65. What’s the implicit name and type of the parameter that gets passed into
the class’ set method?

Value, and it’s data type depends on whatever variable we’re changing.

66. 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++.

67. Does C# support multiple inheritance?
No, use interfaces instead.

68. When you inherit a protected class-level variable, who is it available to?

Classes in the same namespace.

69. 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.

69. 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).

70. C# provides a default constructor for me. I write a constructor that akes 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.

71. What’s the top .NET class that everything is derived from?
System.Object .

72. 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

73. What does the keyword virtual mean in the method definition?
The method can be over-ridden.

74. Can you declare the override method static while the original method is
No, you can’t, the signature of the virtual method must remain the same, only
the keyword virtual is changed to keyword override.
75. 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.

76. 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.

77. Can you allow class to be inherited, but prevent the method from being

Yes, just leave the class public and make the method sealed.

78. 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.

79. 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

80. What’s an interface class?
It’s an abstract class with public abstract methods all of which must be
implemented in the inherited classes.

81. Why can’t you specify the accessibility modifier for methods inside the
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.

82. Can you inherit multiple interfaces?
Yes, why not.
83. 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.

84. 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.

85. How can you overload a method?
Different parameter data types, different number of parameters, different order
of parameters.

86. 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.

87. What’s the difference between System. String and System.StringBuilder
System. String is immutable; System.StringBuilder was designed with the
purpose of having a mutable string where a variety of operations can be

88. How big is the data type int in .NET?
32 bits.

89. How big is the char?
16 bits (Unicode).

90. How do you initiate a string without escaping each backslash?
Put an @ sign in front of the double-quoted string.

91. What are valid signatures for the Main function?
public static void Main ()
public static int Main ()
public static void Main ( string[] args )
public static int Main (string[] args )

92. How do you initialize a two-dimensional array that you don’t know the
dimensions of?
int [ , ] myArray; //declaration
myArray = new int [5, 8]; //actual initialization

93. What’s the access level of the visibility type internal?
Current application.

94. What’s the difference between struct and class in C#?
Structs cannot be inherited.
Structs are passed by value, not by reference.
Struct is stored on the stack, not the heap.

95. Explain encapsulation.
The implementation is hidden, the interface is exposed.

96. What data type should you use if you want an 8-bit value that’s signed?
sbyte .

97. Speaking of Boolean data types, what’s different between C# and /C++?
There’s no conversion between 0 and false, as well as any other number and
true, like in C/C++.

98. Where are the value-type variables allocated in the computer RAM?

99. Where do the reference-type variables go in the RAM?
The references go on the stack, while the objects themselves go on the heap.

100. What is the difference between the value-type variables and reference-
type variables in terms of garbage collection?
The value-type variables are not garbage-collected, they just fall off the stack
when they fall out of scope, the reference-type objects are picked up by GC
when their references go null.

101. How do you convert a string into an integer in .NET?
Int32.Parse( string)
102. How do you box a primitive data type variable?
Assign it to the object, pass an object.

103. Why do you need to box a primitive variable?

To pass it by reference.

104. What’s the difference between Java and .NET garbage collectors?

Sun left the implementation of a specific garbage collector up to the JRE
developer, so their performance varies widely, depending on whose JRE you’re
using. Microsoft standardized on their garbage collection.

105. How do you enforce garbage collection in .NET?

System.GC.Collect ( );

106. Can you declare a C++ type destructor in C# like ~MyClass ()?

Yes, but what’s the point, since it will call Finalize(), and Finalize() has no
guarantees when the memory will be cleaned up, plus, it introduces additional
load on the garbage collector.

107. What’s different about namespace declaration when comparing that to
package declaration in Java?

No semicolon.

108. What’s the difference between const and read only?

You can initialize read only variables to some runtime values. Let’s say your
program uses current date and time as one of the values that won’t change. This
way you declare public read only string DateT = new DateTime ().ToString ().

109. What does \a character do?

On most systems, produces a rather annoying beep.

110. Can you create enumerated data types in C#?

                     111. What’s different about switch statements in C#?

                     No fall-throughs allowed.

                     112. What happens when you encounter a continue statement inside the for

                     The code for the rest of the loop is ignored; the control is transferred back to
                     the beginning of the loop.

                     113. Is goto statement supported in C#? How about Java?

                     Gotos are supported in C# to the fullest. In Java goto is a reserved keyword that
                     provides absolutely no functionality.

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