C# Interview Questions



1. What is C#?

C# is an object-oriented, type-safe, and managed language that is compiled by .Net framework to generate Microsoft Intermediate Language.



2. Can multiple catch blocks be executed?

No, Multiple catch blocks of similar type can’t be executed. Once the proper catch code executed, the control is transferred to the finally block, and then the code that follows the finally block gets executed.



3. What is the difference between public, static, and void?

Public declared variables or methods are accessible anywhere in the application. Static declared variables or methods are globally accessible without creating an instance of the class. Static member are by default not globally accessible it depends upon the type of access modified used. The compiler stores the address of the method as the entry point and uses this information to begin execution before any objects are created. And Void is a type modifier that states that the method or variable does not return any value.



4.What is an object?

An object is an instance of a class through which we access the methods of that class. “New” keyword is used to create an object. A class that creates an object in memory will contain the information about the methods, variables, and behavior of that class.



5. Define Constructors

A constructor is a member function in a class that has the same name as its class. The constructor is automatically invoked whenever an object class is created. It constructs the values of data members while initializing the class.



6. What is Jagged Arrays?

The Array which has elements of type array is called jagged Array. The elements can be of different dimensions and sizes. We can also call jagged Array as an Array of arrays.



7. What is the difference between ref & out parameters?

An argument passed as ref must be initialized before passing to the method whereas out parameter needs not to be initialized before passing to a method.



8. What is the use of ‘using’ statement in C#?

The ‘using’ block is used to obtain a resource and process it and then automatically dispose of when the execution of the block completed.



9. What is serialization?

When we want to transport an object through a network, then we have to convert the object into a stream of bytes. The process of converting an object into a stream of bytes is called Serialization. For an object to be serializable, it should implement ISerialize Interface. De-serialization is the reverse process of creating an object from a stream of bytes.



10. Can we use “this” command within a static method?

We can’t use ‘This’ in a static method because we can only use static variables/methods in a static method.



11. What is the difference between constants and read-only?

Constant variables are declared and initialized at compile time. The value can’t be changed afterward. Read-only is used only when we want to assign the value at run time.



12. What is an interface class? Give one example of it

An Interface is an abstract class which has only public abstract methods, and the methods only have the declaration and not the definition. These abstract methods must be implemented in the inherited classes.



using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace DemoApplication
{
 interface Guru99Interface
 {
  void SetTutorial(int pID, string pName);
  String GetTutorial();
 }

 class Guru99Tutorial : Guru99Interface
 {
  protected int TutorialID;
  protected string TutorialName;

  public void SetTutorial(int pID, string pName)
  {
   TutorialID = pID;
   TutorialName = pName;
  }

  public String GetTutorial()
  {
   return TutorialName;
  }

  static void Main(string[] args)
  {
   Guru99Tutorial pTutor = new Guru99Tutorial();

   pTutor.SetTutorial(1,".Net by Guru99");

   Console.WriteLine(pTutor.GetTutorial());

   Console.ReadKey();
  }
 }
}
				



13. What are value types and reference types?

A value type holds a data value within its own memory space. Example

int a = 30;
				
Reference type stores the address of the Object where the value is being stored. It is a pointer to another memory location.

string b = "Hello There!!";
				



14. What are Custom Control and User Control?

Custom Controls are controls generated as compiled code (Dlls), those are easier to use and can be added to toolbox. Developers can drag and drop controls to their web forms. Attributes can, at design time. We can easily add custom controls to Multiple Applications (If Shared Dlls). So, If they are private, then we can copy to dll to bin directory of web application and then add reference and can use them.

User Controls are very much similar to ASP include files, and are easy to create. User controls can’t be placed in the toolbox and dragged – dropped from it. They have their design and code-behind. The file extension for user controls is ascx.



15. Explain types of comment in C# with examples

i. Single line

Example:

//This is a single line comment";
				

ii. Multiple line (/* */)

Example:

/*This is a multiple line comment
We are in line 2
Last line of comment*/";
				

iii. XML Comments (///).

Example:

/// summary;
/// Set error message for multilingual language.
/// summary;
				





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