Top 50 C# Interview Questions You Need To Know In 2025

Last updated on Nov 27,2024 71.5K Views

Top 50 C# Interview Questions You Need To Know In 2025

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C# is a simple, modern and a general-purpose Object-oriented programming language developed by Microsoft within its .NET framework. In this C# Interview Questions blog, I will introduce you to the most commonly asked Interview Questions in C# and what should be your approach to do the same.

I have categorized the questions into three sections:

Let’s get started.

Beginner’s Level

Q1. List down the differences between Public, Static and void keywords?

Ans-

KeywordDescription

Public

It is an access specifier which states that the method of a class can be accessed publicly

Static

It is a keyword used for declaring a member of a type, specific to that type

void

It states that the method does not return any value
using System;
class test
{
static void main(String args[])// main is the method that gets executed first
{
Console.Writeline("Welcome to the world of C#");
}
}

Q2. Define C# and list the features.

Ans- C# is an object-oriented, typed safe and manage language that is compiled by .NET framework and was developed by Microsoft back in 2000. The idea was that it will be used in the development of all kinds of software aiming at different platforms like Windows, Web, mobile using only one programming language. Fast forward to the present day it is one of the most popular programming languages worldwide, millions of developers use this language to build all kinds of software.

Some of the features of C#(sharp) are:

Let’s move on to the next question,

Q3. List down the reason behind the usage of C# language.

Ans-  There are several reasons for the usage of C# as a programming platform. Some of them are listed below.

Q4. What are the advantages of using C#?

Ans-  Following are the advantages of using C#:

Q5. What are the different types of comments in C#?

Ans- Below listed are the types of comments followed in C#:

a. Single line comments

// hello, this is a single line comment

b. Multiline comments

  /* Hello this is a multiline comment
   last line of comment*/

c. XML comments

/// Hello this is XML comment

Q6. Illustrate the process of code compilation in C#?

Ans-  There exist four steps in the process of code compilation:

  1. Compilation of Source code in managed  code
  2. Clubbing the newly created code into assembly
  3. Loading the CLR (Common Language Runtime)
  4. Execution of assembly through CLR

Q7. List down the access modifiers available in C#.

Ans- Following are the access modifiers available for general use:

Moving ahead in C# Interview questions, let’s unfold some functionalities used in C#.

Q8. List down the different IDE’s Provided by Microsoft for C# Development.

Ans- Below listed are few IDE’s for C# development:

Q9. Distinguish between Continue and Break Statement?

Ans- Using break statement you can ‘jump out’ of the loop whereas while making use of continue statement you can jump over an iteration and continue the loop execution.

Example (Break Statement):

using System;
using System.Collections;
using System.Linq;
using System.Text;

namespace break_example{
Class break_Stmnt{
public static void main(String args[]){
for(int i=0;i<=6;i++)
{
if(i==5)
{
break;
}
Console.Readline("The number is +i");
}
}
}

Output:

the number is 0;
the number is 1;
the number is 2;
the number is 3;
the number is 4;

Example (Continue Statement):

using System;
using System.Collections;
using System.Linq;
using System.Text;

namespace continue_example{
Class continue_Stmnt{
public static void main(String args[]){
for(int i=0;i<=6;i++)
{
if(i==5)
{
continue;
}
Console.Readline("The number is +i");
}
}
}

Output:

the number is 0;
the number is 1;
the number is 2;
the number is 3;
the number is 5;

Q10. What are the different approaches of passing parameters to a method?

Ans- There are three ways of passing parameters to a method:

Value Parameters-  Under this method the actual value of an argument is copied to the formal parameter of the function. In, this case the changes made into the formal parameter of the function have no effect on the actual value of the argument.

Reference Parameters- This method copies the argument referring to the memory location into the formal parameter. Meaning changes made to the parameter affect the argument.

Output Parameters- This method returns more than one value.

 Let’s move ahead in C# Interview Questions and see the next category.

Intermediate level C# Interview Questions

Q11. Distinguish between finally and finalize blocks?

Ans- finally block is called after the execution of try and catch blocks, It is used for exception handling whether or not the exception has been caught this block of code gets executed. Generally, this block of code has a cleaner code.

The finalize method is called just before the garbage collection. Main priorities are to perform clean up operation for unmanaged code, it is automatically invoked when an instance is not subsequently called.

Q12. What is Managed or Unmanaged Code?

Ans- Managed code is one which is executed by CLR (Common Language Runtime) in simple terms it means all the application code is dependent on the .NET platform, considered as overseen in view of them. Unmanaged code is any code that is executed by runtime application of some other structure different from .NET platform. The runtime of application will deal with memory, security and other execution activities.

Q13. What is an Object?

Ans- Object is an instance of a class, It is used for accessing the methods of a class. “New” keyword is used for the creation of an object, a class that creates an object in the memory location contains the information about methods, variables, and behavior of that class.

To know more about Object in Java, Python, and C++ you can go through the following blog:

Q14. What is a Class?

Ans- A class is a blueprint of an object. It defines different kinds of data and functionalities objects will have. A class enables you to create your own custom types by clubbing together variables of different types, methods, and events. In C# a class is defined by a class keyword.

To know more about Class in Java, Python, and C++ you can go through the following blog:

Q15. Define an abstract class?

Ans- It is a type of class whose objects can’t be instantiated, It contains something like a single approach or technique and indicated by the keyword ‘abstract’.

To know more about  abstract class in Java you can go through the following blog:

Q16. Define sealed classes in C#?

Ans- You create sealed classes in situations when you want to restrict the class to be inherited. For doing this sealed modifiers are used. If you forcefully specify a sealed class as a base class then a compilation error occurs.

Q17. Define a Partial class?

Ans- A partial class is the only one that essentially splits the definition of a class into multiple classes in either same source code files or multiple source code files. One can create a class definition in multiple files but that is compiled as one class at run-time and when an instance of this class is created, one can access all methods from every source file with the same object. It is indicated by the keyword ‘partial’.

Q18. List down the fundamental OOP concepts?

Ans- There are four fundamental OOP (Object Oriented Programming) concept they are listed as follows:

To know more about OOPs in Java, Python, and C++ you can go through the following blogs:

Q19. Explain the process of inheriting a class into another class?

Ans- Colon is used as an inheritance operator in C#. Place the colon and the class name.

public class Derivedclass: childclass

Q20. Define method overloading in C#?

Ans- Method overloading essentially is creating multiple methods with the same name and unique signatures with the same class. When you
compile, the compiler makes use of overload resolution to determine the specific method which will be invoked.

Q21. List the differences between method overriding and method overloading?

Ans- Under Method overriding the definition of the derived class is changed which in turn changes the method behavior. Method overloading is simply creating a method with the same name under the same class under different signatures.

Q22. Explain StreamReader/StreamWriter class?

Ans- Streamreader and StreamWriter are classes of namespace.System.IO. Used when we want to read or write charact90, Reader based data,
respectively.

members of StreamReader are: close(), Read(), Readline().
members of Streamwriter are: close(), write(), writeline().

Example program:

Class Testprogram
{
using(StreamReader sr = new StreamReader("C:Readme.txt")
{
// Any code to read//
}
using(StreamWriter sr = ndew StreamWriter("C:Readme.txt")
{
// Any code to write//
}
}

Q23. What is an Interface?

Ans- An Interface is basically a class with no implementation. It contains only the declaration of properties, attributes, and events.

Q24. Distinguish between a class and struct?

Ans- Given below are the differences between a class and struct:

Class

Struct

It supports inheritance

It does not support inheritance

It is Pass by reference

It is pass by value

Members are private by default

Members are public by default

Considered good for larger complex objects

Considered good for small models

Q25. List the difference between the Virtual method and the Abstract method?

Ans- A Virtual method must always have a default implementation. However, it can be overridden in a derived class by the keyword override.

An Abstract method doesn’t have any implementation. It resides in the abstract class, and also it is mandatory that the derived class must implement abstract class. Use of override keyword is not necessary.

Q26. Illustrate Namespaces in C#?

Ans- Namespaces are used for organizing large code projects. “System” is one of the most popular and widely used namespaces in C#. One can create their own namespace and use one into another called nesting.

Q27. Define using statement in C#?

Ans- “Using” keyword simply denotes that the particular namespace is being used by the program. For ex- using System, Here System is a namespace. The class console is defined under system, so we can use the Console.Writeline(…) or Readline in our program.

Q28. Define an Escape Sequence, Name few strings in Escape Sequence?

Ans-  An Escape Sequence is denoted by a backslash (). The backslash merely indicates that the character it is following should be interpreted literally or is a special character. An escape sequence is a single character.

Few escape sequences are as follows:

n – newline character

b – backspace

– backlash

‘ – Single quote

” – Double quote

Q29. Define Boxing and Unboxing in C#?

Ans- Converting a value type to the reference type is called boxing.

Example:

int value = 10
//-------Boxing--------//
object boxedvalue = value1;

Explicit conversion of the same reference type i.e. converting it back to the value type is called Unboxing.

Example:

 //----------------Unboxing-------// int UnBoxing = int(boxedvalue);

To know more about Boxing and Unboxing in Java you can go refer this article- Boxing in Java. 

Q30. Define an array?

Ans- An array is used to store multiple variables of the same type. Collection of variables stored in a contiguous memory location.

Example:
double numbers = new double[10];
int[] Score = new int[4] {25,24,23,22,21,20}

Above given example above is of a Single Dimensional array. It is a linear array where values are stored in a single row. A multidimensional array is the one having more than one dimension. A good example would be of a rectangle.

Example:

int[,] numbers = new int[4,3]{ {1,2} {2,3} {3,4} {4,5} };

To know more about arrays in Java, Python , and C++ you can go through the following blogs:

Q31. Define a Jagged Array in C#?

Ans- A Jagged array is referred to as an “array of arrays”. It is an array whose elements are arrays, the element of the same can be of different dimensions and sizes. The length of each array index can differ.

Example:

int[][] jagArray = new int[5][];

Q32. Distinguish between Array and Arraylist in C#?

Ans-

ArrayArrayList

 Array uses the vector array for storing the elements

ArrayList uses the LinkedList to store the elements

Size of the Array must be defined until redim used(vb)

There’s no need for specifying storage size.

An array is a specific data type storage

ArrayList can store everything as an object

Typecasting is not necessary

Typecasting is necessary

There is no RunTime exception

There is a RunTime error exception

Elements can’t be inserted or deleted in between

Elements can be inserted or deleted in between

Q33. Define Collections?

Ans- A collection essentially works like a container for instances of other classes. Every class implements Collection Interface.

To know more about collections in Java, check out the following blog:

Q34. Write a short note on Interface?

Ans- An Interface is a class with no implementation. It consists of a declaration of methods, Parameters, and values.

To know more about Interface in Java, check out the following blog:

Moving on in C# Interview Question let’s see the next category.

Advance Level

Q35. Illustrate Serialization?

Ans- A process that involves converting some code into its binary format is known as a serialization in C#. In doing so it gives the flexibility where code can be stored easily and or written to a disk or some other storage device. Serialization is used when there is a strict need for not losing the original code.

Serialization in C# is of three types:

Binary Serialization- It is fast and demands less space, converts any code into its binary format. Serialize and restore public and non-public properties.

SOAP- Generates a complete SOAP compliant envelope used by any system by its ability to understand SOAP. Classes under this type of Serialization reside in System.Runtime.Serialization. 

XML Serialization- It serializes all the public properties to XML document. Readability being one factor, an XML document can also be manipulated in various ways. Classes under this type reside in System.sml.Serialization.

To know more about Serialization in Java, check out the following blog:

Q36. Define Parsing? Explain how to Parse a DateTime String?

Ans- Parsing is a method of converting a string into another data type.

Example:

string text = "200";
int num = int.Parse(text);

In the above-given example, 200 is an integer. So, the Parse method converts the string 200 into its own base type, i.e. int.
To parse a DateTime String let’s see a small example.

Example:

 string dateTime = "Aug 26,2019"; Datetime parsedvalue = Datetime.Parse(dateTime);

Q37. Define Delegate?

Ans- Delegate is a variable that holds the reference to a method. It is a function pointer of the reference type. All Delegates are derived from the
System.Delegate namespace. Both Delegate and the method that it refers to can have the same signature. Let’s see a small example.

Example:

public Delegate int myDel(int number); //declaring a delegate
public class Program
{
public int SubstractNumbers(int a) //Class Program has the method same signature as delegate called  
{
int difference = a - 10;
return difference;
}
public void start()
{
myDel DelegateExample = SubstractNumbers;
}
}

Q38. Distinguish between System.String and System.Text.StringBuilder classes?

Ans – System.String is immutable. Whenever you modify the value of a string variable then a new memory is allocated to the new value and previous memory allocation is released. System.Text.StringBuilder is mutable i.e. supports the fact that a variety of operations can be performed
without allocating a seperate memory location for the already modified string.

Q39. Illustrate the differences between the System.Array.CopyTo() and System.Array.Clone()?

Ans – Using the Clone() method, a new array object is created containing all elements of the original array. Using the CopyTo() method all the elements of the existing array gets copied into another existing array. Both use a shallow copy method.

Q40. Write the Syntax for catching an exception in C#?

Ans – To catch an Exception we make use of try-catch blocks. The catch block has a parameter of the system.Exception type.

Example:

try
{
GetAllData();
}
catch(Exception ex){
}

Q41. Explain about generics in C#.NET?

Ans- Generics are used to make reusable code classes which decrease the code redundancy,

Q42. List down the differences between “dispose” and “finalize” methods in C#.

Ans- Dispose() is called when we want an object to release unmanaged resources with them. Whereas, Finalize() is used for the same purpose but
it doesn’t assure garbage collection of an object.

Q43. Define C# I/O classes? List the commonly used classes?

Ans- C# consists of System.IO namespace which has classes that compute and perform various operations on files like creating, deleting, opening
and closing etc.

Few commonly used I/O classes are listed below:

File- Helps in manipulating file.
StreamWriter- Generally used for writting characters to a stream.
StreamReader- Generally used for reading characters to a stream.
StringWriter- Used for writing a string buffer.
Stringreader- Used for reading a string buffer.

Q44. Define thread? Explain about Multithreading?

Ans- Thread is a set of instructions that when executed enables the program to perform concurrent processing. Concurrent processing helps in doing more than one process at a time. By default, C# consists of only thread. Other threads can be created to execute the code in parallel with original thread.

Thread follows a life cycle where it starts whenever a thread is created and gets terminated immediately after the execution. The namespace it follows is System.Threading which has to be included to create threads and use its members.

Threads are created by extending the thread class. Start() method marks the beginning of the thread execution.

//callThread is our target method//
ThreadStart methodThread = new ThreadStart(CallThread);
Thread childThread = new Thread(methodThread);
childThread.start();

C# can also execute more than proceeses/task at a time which is done by handling different processes at different time labeled as “multithreading”.
Several operations of the same are listed below:

To know more about Threads in Java, you can go through the following blog:

Let’s move on in C# Interview Questions and see the next question.

Q45. What are Events?

Ans- Events in C# follow a concept where it consists of a Publisher, Subscriber, Notification and a handler. You can think of an event as nothing but an encapsulated delegate.

Example:

public Delegate void TestEvent();
public TestEvent TestEvent1;

Q46. Explain Synchronous and Asynchronous Operations?

Ans- Synchronization is a way of creating a thread-safe code where only a single thread will access the code in a given time. A synchronous call waits for completion of method and then continous the program flow. Synchronous programming adversely affects the UI operations that normally happens when user tries to perform time-consuming operations since only one thread is used.

In Asynchronous operation, the method call immediately returns allowing the program to perform other operations while the method called completes its share of work in certain circumstances.

Q47. Explain Async and Await?

Ans- Async and Await keywords are mostly used for creating asynchronous methods in C#. Usage of the same is shown through an example:

public async Task>CalculateCount()
{
await Task.Delay(2000);
return 1;
}
public async task mytestmethod()
{
Task> count = CalculateCount();
int result = await count;
}

In the above-given code async keyword is used for method declaration. The Count is of a task type int which calls the method CalculateCount(). CalculateCount() starts execution and calculates something.

Q48. Explain Deadlock?

Ans- A deadlock is a situation that arises when a process isn’t able to complete it’s execution because two or more than two processes are waiting for each other to finish. This usually occurs in multi-threading. In this, a shared resource is being held up by a process and another process is waiting for the first process to get over or release it, and the thread holding the locked item is waiting for another process to complete.

Q49. Illustrate Race Condition?

Ans-  A Race Condition occurs in a situation when two threads access the same resource and try to change it at the same time. The thread which accesses the resource first cannot be predicted. Let me take a small example where two threads X1 and X2 are trying to access the same shared resource called T. And if both threads try to write the value to T, then the last value written to T will be saved.

Q50. What is Thread Pooling?

Ans- A Thread pool is a collection of threads that perform tasks without disturbing the primary thread. Once the task is completed by a thread it returns to the primary thread.

This brings us to the end of this article on C# Interview Questions. I hope it helped in adding up to your knowledge. Wishing you all the best for your interview. Happy learning.

In case you are looking for the most common Technical Interview Questions, read along:

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