Interview questions for .NET

.NET interview questions
What is a static class?
What is static member?
What is static function?
What is static constructor?
How can we inherit a static variable?
How can we inherit a static member?
Can we use a static function with a non-static variable?
How can we access static variable?
Why main function is static?
How will you load dynamic assembly? How will create assesblies at run time?
What is Reflection?
If I have more than one version of one assemblies, then how will I use old version (how/where to specify version number?) in my application?
How do you create threading in.NET? What is the namespace for that?
What do you mean by Serialize and MarshalByRef?
What is the difference between Array and LinkedList?
What is Asynchronous call and how it can be implemented using delegates?
How to create events for a control? What is custom events? How to create it?
If you want to write your own dot net language, what steps you will you take care?
Describe the diffeerence between inline and code behind - which is best in a loosely coupled solution?
How dot net compiled code will become platform independent?
Without modifying source code if we compile again, will it be generated MSIL again?
How does you handle this COM components developed in other programming languages in.NET?
How CCW (Com Callable Wrapper) and RCW (Runtime Callable Wrappers) works?
What are the new thee features of COM+ services, which are not there in COM (MTS)?
What are the differences between COM architecture and.NET architecture?
Can we copy a COM dll to GAC folder?
What is Shared and Repeatable Inheritance?
Can you explain what inheritance is and an example of when you might use it?
How can you write a class to restrict that only one object of this class can be created (Singleton class)?
What are virtual destructures?
What is close method? How its different from Finalize and Dispose?
What is Boxing and UnBoxing?
What is check/uncheck?
What is the use of base keyword? Tell me a practical example for base keyword’s usage?
What are the different.NET tools which you used in projects?
What will do to avoid prior case?
What happens when you try to update data in a dataset in.NET while the record is already deleted in SQL Server as backend?
What is concurrency? How will you avoid concurrency when dealing with dataset?
One user deleted one row after that another user through his dataset was trying to update same row. What will happen? How will you avoid this problem?
How do you merge two datasets into the third dataset in a simple manner?
If you are executing these statements in commandObject. “Select * from Table1; Select * from Table2″ How you will deal result set?
How do you sort a dataset.
If a dataset contains 100 rows, how to fetch rows between 5 and 15 only?
What is the use of Parameter object?
How to generateXML from a dataset and vice versa?
How do you implement locking concept for dataset?
How will you do Redo and Undo in TextBox control?
How to implement DataGrid in.NET? How would you make a combo-box appear in one column of a DataGrid? What are the ways to show data grid inside a data grid for a master details type of tables? If we write any code for DataGrid methods. what is the access specifier used for that methods in the code behind file and why?
How can we create Tree control in asp.NET?
Write a program in C# to find the angle between the hours and minutes in a clock?
Write a program to create a user control with name and surname as data members and login as method and also the code to call it.
How can you read 3rd line from a text file?
Explain the code behind wors and contrast that using the inline style.
Explain different types of HTML, Web and server controls.
What are the differences between user control and server control?
How server form post-back works?
Can the action attribute of a server-side
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tag be set to a value and if not how can you possibly pass data from a form page to a subsequent page?
How would ASP and ASP.NET apps run at the same time on the same server?
What are good ADO.NET object to replace to ADO Recordset object.
Explain the differences between Server-side code and Client-side code.
What type of code(server or client) is found in a Code-Behind class?
Should validation (did the user enter a real date) occur server-side or client-side? Why?
What does the “EnableViewState” property do? Why would I want it on or off?
What is the difference between Server.Transfer and response.Redirect? Why?
Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced.NET component?
Let’s say I have an existing application written using VB6 and this application utilizes Windows 2000 COM+ transaction services. How would you approach migrating this application to.NET?
If I am developing an application that must accomodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing). What would be the best approach to maintain login-in state for the users?
What are ASP.NET web forms? How is this technology different than what is available though ASP(1.0-3.0)?
How does VB.NET achieve polymorphism?
How does C# achieve polymorphism?
Can you explain what is Inheritance and an example in VB.NET and C# of when you might use it?
Describe difference between inline and code-behind?
What is loosely coupled solution in.NET?
What is diffgram?
Where would you use an iHTTPModule and what are the limitations of any approach you might take in implementing one?
What are the Advantages and DisAdvantages of viewstate?
Describe session handling in a webform, how does it work and what are the limitations?
How would you get ASP.NET running in Apache web servers? Explain it’s limitations.
What is MSIL and why should my developers need an appreciation of it if at all?
Which methos do you invoke on the DataAdapter control to load your generated dataset with data?
Can you edit data in Repeater control? How?
Which template must you provide, in order to display data in a Repeater control?
How can you provide an alternating color scheme in a Repeater control?
What property must you set, and what method must you call in your code, in order to bind the data from some data source to the repeater control?
What base class do all web forms inherit from?
What method do you use to explicitly kill a user’s session? How?
How do you turn off cookies for one page in your site? Give an example.
Which two properties are on every validation control?
What tags do you need to add within the asp:datagrid tags to bind columns manually? Give an example.
How do you create a permanent cookie?
What tag do you use to add a hyperlink column to the dataGrid?
What is the standard you use to wrap up a call to a Web Service?
Which method do you use to redirect the user to another page without performing a round trip to the client? How?
What is the transport protocol you use to call a Seb Service SOAP?
What does WSDL stand for?
What property do you have to set to tell the grid which page to go to when using the Pager object?
Where on the Internet would you look for Web Services?
What tags do you need to add within the asp:datagrid tags to bind columns manually? How?
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?
How is a property designated as read-only?
Which control would you use if you needed to make sure the values in two different controls matched?
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1. ishaq said,
I want to knowwhat is multiple inheritance?what is Virtual polymorphism?how to fetch 5th and 15th record from the datagrid using c#.net?
2. vishal said,
can we write c# code in web.config file?can we bind datagrid with datareader?can we add two web.config in one project?
3. Haris Habib said,
what is multiple inheritance?The way to inherit a class from multiple classes.In C++ that was possible but not in C# and Vb.Net.Although you can Inherit/Implement from multiple interfaces.
4. Ali Baba said,
to fetch the records from any row just use the following technique:
datagrid.rows[n].columns[m]where n is the row number and m is the column number
to fetch from gridview:gridview.rows[n].ItemArray[m]
5. Ahmed said,
1. What is a static class?A static class is a class which can not be instantiated using the ‘new’ keyword. They also only contain static members, are sealed and have a private constructor.
2. What is static member?A static member is a method, field, property or event that can be called without creating an instance of its defining class. Static members are particularly useful for representing calculations and data that are independent of object state.
3. What is static function?A static function is another term for a static method. It allows you to execute the function without creating an instance of its defining class. They are similar to global functions. An example of a static function could be: ConvertFromFarenheitToCelsius with a signature as follows:
public static double ConvertFromFarenheitToCelsius (string valToConvert){//add code here}
4. What is static constructor?A static constructor has a similar function as a normal constructor i.e. it is automatically called the first time a class is loaded. The differences between a conventional constructor are that it cannot be overloaded, cannot have any parameters nor have any access modifiers and must be preceded by thekeyword static. In addition, a class with a static constructor may only have static members.
5. How can we inherit a static variable?6. How can we inherit a static member?When inheriting static members there is no need to instantiate the defining class using the ‘new’ keyword.
public class MyBaseClass{MyBaseClass(){}public static void PrintName(){}
}
public class MyDerivedClass : MyBaseClass{MyDerivedClass (){}
public void DoSomething(){MyBaseClass.GetName();}
}
7. Can we use a static function with a non-static variable?No.
8. How can we access static variable?By employing the use of a static member field as follows:public class CashSales{//declare static member fieldprivate static int maxUnitsAllowed = 50;
//declare method to return maximum number of units allowed
public static int GetMaxUnitsAllowed (){Return maxUnitsAllowed;}
}The static field can now be accessed by simply doing CashSales.GetMaxUnitsAllowed(). No need to create an instance of the class.
9. Why main function is static?Because it is automatically loaded by the CLR and initialised by the runtime when the class is first loaded. If it wasn’t static an instance of the class would first need to be created and initialised.
10. How will you load dynamic assembly? How will create assemblies at run time?
Load assembly:By using classes from the System.Reflection namespace.Assembly x = Assembly.LoadFrom( “LoadMe.dll” );
Create assembly;Use classes from System.CodeDom.Compiler;
11. What is Reflection?The System.Reflection namespace provides us with a series of classes that allow us to interrogate the codebase at run-time and perform functions such as dynamically load assemblies, return property info e.t.c.
12. If I have more than one version of one assembly, then how will I use old version (how/where to specify version number?) in my application?The version number is stored in the following format: …. The assembly manifest can then contain a reference to which version number we want to use.
13. How do you create threading in.NET? What is the namespace for that?
System.Threading;
//create new thread using the thread class’s constructor
Thread myThread = new Thread(new ThreadStart (someFunction));
14. What do you mean by Serialize and MarshalByRef?Serialization is the act of saving the state of an object so that it can be recreated (i.e deserialized) at a later date.The MarshalByRef class is part of the System.Runtime.Remoting namespace and enables us to access and use objects that reside in different application domains. It is the base class for objects that need to communicate across application domains. MarshalByRef objects are accessed directly within their own application domain by using a proxy to communicate. With MarshalByValue the a copy of the entire object is passed across the application domain
15. What is the difference between Array and LinkedList?An array is a collection of the same type. The size of the array is fixed in its declaration.A linked list is similar to an array but it doesn’t have a limited size.
16. What is Asynchronous call and how it can be implemented using delegates?A synchronous call will wait for a method to complete before program flow is resumed. With an asynchronous call the program flow continues whilst the method executes.
//create objectSomeFunction objFunc = new SomeFunction();
//create delegateSomeDelegate objDel = new SomeDelegate(objFunc.FunctionA);
//invoke the method asynchronously (use interface IAsyncResult)IAsyncResult asynchCall = SomeDelegate.Invoke();
17. How to create events for a control? What is custom events? How to create it?An event is a mechanism used in a class that can be used to provide a notification when something interesting happens. (typical evens in a windows application include: change text in textbox, double click or click a button, select an item in dropdown box).
A custom event is an event created by the user that other developers can use. For example assuming that we have a CashTransaction class and we have a bank balance property in that class. We may want to set-up an event that provides a notification when the bank balance drops below a certain amount. In order to produce an event the process would be roughly as follows:
Create the class for the event derived from EventArgs.Create a delegate with a return type of void.Create a class containing the method that will activate the event.Create a class with methods to handle the event.
18. If you want to write your own dot net language, what steps you will you take care?We will need to ensure that the high level code is compiled to MSIL (Microsoft intermediate language) so that it can be interpreted by the CLR.
19. Describe the difference between inline and code behind - which is best in a loosely coupled solution?The term ‘code behind’ refers to application code that is not embedded within the ASPX page and is separated out into a separate file which is then referenced from the ASPX page. Inline code is the traditional ASP architectural model where business logic code was embedded within the ASP page. Separating the business logic code from the presentation layer offers several advantages:
1) It allows graphic designers and web developers to work on the presentation layer whilst the application developers concentrate on the business logic.2) The codebehind file is compiled as a single dll increasing the efficiency of the application,3) The codebehind model offers a true OO development platform,4) It speeds up development time as it allows developers to fully maximise the features of the .NET framework such as Cahing, ViewState, Session, Smart Navigation etc.5) Code is much easier to maintain and susceptible for change.6) The compiler and VS.NET provides much better support for error checking, intellisense and debugging when using the code behind model.
20. How dot net compiled code will become platform independent?The raison d’etre for .NET was to cater for multiples languages on a single windows platform whereas the aim of Java was to be a single language on multiple platforms. The only way that .NET can be platform independent is if there is a version of the .NET framework installed on the target machine.
21. Without modifying source code if we compile again, will it be generated MSIL again?No.
22. How does you handle this COM components developed in other programming languages in.NET?use TlbImp.exe to import the COM types into your .NET project. If no type library for the COM component then use System.Runtime.InteropServices
22. How does you handle this COM components developed in other programming languages in.NET?use TlbImp.exe to import the COM types into your .NET project. If no type library for the COM component then use System.Runtime.InteropServicesuse RegAsm.exe to call a .NET developed component in a COM application.
23. How CCW (Com Callable Wrapper) and RCW (Runtime Callable Wrappers) works?CCW: When a COM application calls a NET object the CLR creates the CCW as a proxy since the COM application is unable to directly access the .NET object.RCW: When a .NET application calls a COM object the CLR creates the RCW as a proxy since the .NET application is unable to directly access the .COM object.
24. What are the new thee features of COM+ services, which are not there in COM (MTS)?Role based security.Neutral apartment threading.New environment called context which defines the execution environment
25. What are the differences between COM architecture and.NET architecture?.Net architecture has superseded the old COM architecture providing a flexible rapid application development environment which can be used to create windows, web and console applications and web services. .NET provides a powerful development environment that can be used to create objects in any .NET compliant language. .NET addresses the previous problems of dll hell with COM by providing strongly named assemblies and side-by-side execution where two assemblies with the same name can run on the same box.
26. Can we copy a COM dll to GAC folder?No. It only stores .NET assemblies.
28. Can you explain what inheritance is and an example of when you might use it?Inheritance is a fundamental feature of any OO language. It allows us to inherit the members and attributes from a base class to a new derived class. This leads to increased code reusability and also makes applications easier to develop, maintain and extend as the new derived class can contain new features not available in the base class whilst at the same time preserving the attributes inherited from the base class.
29. How can you write a class to restrict that only one object of this class can be created (Singleton class)?Use the singleton design pattern.public sealed class Singleton{static readonly Singleton Instance=new Singleton();
static Singleton(){}
Singleton(){}
public static Singleton Instance{get{return Instance;}}}
30. What are virtual destructors?A constructor can not be virtual but a destructor may. Use virtual destructors when you want to implement polymorphic tearing down of an object.
31. What is close method? How it different from Finalize and Dispose?finalise is the process that allows the garbage collector to clean up any unmanaged resources before it is destroyed.The finalise method can not be called directly; it is automatically called by the CLR. In order to allow more control over the release of unmanaged resources the .NET framework provides a dispose method which unlike finalise can be called directly by code.Close method is same as dispose. It was added as a convenience.
32. What is Boxing and UnBoxing?Boxing is the process of converting a value type to a reference type. More specifically it involves encapsulating a copy of the object and moving it from stack to heap. Unboxing is the reverse process.
33. What is check/uncheck?checked: used to enable overflow checking for arithmetic and conversion functions.unchecked: used to disable overflow checking for arithmetic and conversion functions.