Top 21 C# Interview Questions and Answers for 2025

1. Which are the four steps involved in the C# code compilation?

Here are four steps of code compilation in C#:

• Source code compilation in ‘Managed code.’
• Newly created code gets clubbed with assembly code.
• The Common Language Runtime (CLR) gets loaded.
• Assembly execution goes through CLR.

2. Which are the various ways to pass parameters in a method?

The various ways of passing parameters in a method include:

• Output parameters: Let the method return more than one value.
• Value parameters: The formal value copies and saves the value of the actual argument, allowing the formal parameter to be changed without impacting the actual parameter’s value. 
• Reference parameters: The formal argument preserves the actual parameter’s memory address, thus any change to the formal parameter will affect the actual argument as well.

3. What are Managed and Unmanaged codes?

‘Managed code’ refers to code that is executed by the Common Language Runtime or CLR. The .Net framework, which employs the garbage collector internally to clear up unwanted memory, gives it the name ‘Managed code.’

‘__Unmanaged code’ is executed by a framework other than .Net runtime or outside the .Net framework.

4. What is a Class and an Object in C#?

A ‘Class’ is a set of methods and properties that represent a real-time entity. All of the actions are grouped together in a class.

An ‘Object’ is a block of allocated memory that can be saved as Variables, Arrays, or Collections.

5. Where are the steps of Code compilation in C#?

Code compilation has four steps which include:

• Compiling ‘Source code’ to ‘Managed code’ using C# compiler.
• Executing the assembly by CLR.
• Combining the new code into assemblies.
• Loading the CLR.

6. Explain the difference between the Virtual method and the Abstract method

Virtual methods require a default implementation. However, there is no implementation for an Abstract method. 

7. What is an Escape Sequence? Name the sequences in C#.

A backslash denotes an escape sequence (\). The backslash denotes that the character after the backslash is a special character. A single character is considered an escape sequence.

8. What is Serialization?

Serialization converts a code to its binary format. Serialization can be readily saved and written to a disc after being converted to bytes.

Serializations are useful for preserving the original version of the code and retrieving it afterwards. 

9. Differentiate between Continue Statements and Break?

Here is the difference between Break and Continue statements:

• Continue statement: Used to jump to the next iteration of the loop after skipping a particular iteration. 
• Break statement: Used to exit the loop by skipping the next statements of the current iteration.

10. What is the difference between finalize and finalize blocks?

The Finalize block is called after the try and catch blocks have been completed. This block of code gets executed regardless of the exception that has been caught.

The Finalize method is called just before garbage collection. The Finalize method’s top priority is to clear unmanaged code, which is triggered automatically anytime an instance isn’t recalled.

11. What is a Partial Class?

C# allows developers to split a single class file into numerous physical files. To do so, they need to employ the Partial. This capability assists developers in breaking down large class files into several little physical files.

12. Can you differentiate between method overriding and method overloading?

Method overriding changes the definition of the derived class, which changes the behavior of the method.

Under the same class, method overloading is the process of defining the same name method with several signatures.

13. What is a constructor, and what are its different types?

A constructor is a unique method with the same name as the class. Even if a constructor is not ready, the compiler creates a default constructor in memory at the time of creating an object of the class. The constructor initializes the object with some default values. Constructor types include default, parameterized, copy, static, and private constructors.

14. What is a destructor in C#?

The garbage collector automatically manages a destructor, clearing memory to free up resources. Internally, System.GC.collect() is used for this function. If necessary, a destructor can explicitly clear memory to free up resources.

15. What is inheritance?

Inheritance is a feature of object-oriented programming that allows developers to create a base class with defined functionality, such as data and behavior, and create derived classes that inherit or override that functionality.

16. Explain the steps to implement multiple interfaces with the same method name in the same class.

This is a trick question. Though the implementation is possible, developers will avoid doing it. A knowledgeable candidate might say: “I would avoid implementing several interfaces with the same method name within the body of the function. Instead, the name of the interface would be explicitly provided in the method’s body. The compiler will figure out which interface methods are being used, addressing the problem.” 

17. What is a sealed class?

When there is no need to inherit a particular class further, or it is necessary to prevent that particular class from being inherited, the class is turned into a sealed class. To make a sealed class, developers use the ‘sealed’ keyword.

18. What is enum?

An enum is a value type. Enum functions as an enumerated list, which is a collection of connected constants. The types of enums are int, float, double, and byte.

To generate a numeric constant, developers use the .NET framework enum. The enumeration element’s default value is int. The first enumerator has the value 0 by default and each subsequent enumerator increases by one like an array.

Here is a sample syntax: enum Day {Mon, Tue, Wed, Thu, Fri, Sat, Sun};

19. What is serialization?

If developers wish to send an object across a network, they will have to turn it into a stream of bytes. The process of transforming an item into a stream of bytes is known as serialization. 

20. What is multithreading?

A thread is a process that runs any code block in C#. A thread is the program’s execution path. Simple programs can run in a single thread, but most modern programs employ multithreading.

Multithreading divides a process’s execution into numerous threads, allowing it to run simultaneously and more efficiently. Multithreading also allows developers to run multiple tasks at the same time. 

21. What are generics in C#?

Generics in C# include four action items which are as follows:   

• Increase performance.
• Increase type safety.
• Reduce repeated code.
• Make reusable code.

By practicing these 21 questions, you can thoroughly understand the key concepts in the C# programming language. The questions can help you conduct or give C# interviews effectively. 

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What is C# NET programming?
The computer language C# (pronounced “See Sharp”) is modern, object-oriented, and type-safe. Developers can create a wide range of safe and robust .NET applications using C#. C# comes from the C family of languages.

What are all the C# important topics for an experienced interview?
Here are the important topics for a C# interview:

• .NET Framework
• CLR
• CLS
• CTS
• Classes & Objects
• Concepts of OOPs (Encapsulation, Inheritance, Polymorphism, Abstraction)
• Difference between Abstract & Interface

What should I know about the C# Interview?
C#’s popularity has increased dramatically over the past few years. This programming language’s environment is thriving. C# is used by programmers to build websites, custom software, games, and mobile apps. 

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