Top C# Interview Questions and Answers

Published: June 2026 | Category: Career & C# Development | Reading Time: 18 Minutes

Technical interviews can be challenging, especially when applying for .NET development roles. Employers often evaluate both theoretical knowledge and practical coding skills.

This guide covers commonly asked C# interview questions, explanations, and sample answers that can help you prepare for junior, mid-level, and senior developer positions.


Topics Covered
  • C# Fundamentals
  • Object-Oriented Programming
  • Collections
  • LINQ
  • Exception Handling
  • Delegates and Events
  • Async and Await
  • Tasks and Multithreading
  • Entity Framework Core
  • ASP.NET Core
  • Common Interview Tips

1. What Is C#?

C# is a modern object-oriented programming language developed by Microsoft. It is widely used for web applications, desktop software, cloud services, APIs, mobile applications, and games.

2. What Is the Difference Between Value Types and Reference Types?

Value Type Reference Type
Stores actual data Stores reference to data
Allocated on stack Allocated on heap
Examples: int, bool Examples: string, class

3. What Are the Four Pillars of OOP?

  • Encapsulation
  • Inheritance
  • Polymorphism
  • Abstraction

4. What Is the Difference Between Abstract Classes and Interfaces?

Abstract classes can contain both implemented and abstract members, while interfaces define contracts that classes must implement.

5. What Is LINQ?

LINQ (Language Integrated Query) allows developers to query collections, databases, XML documents, and other data sources using a consistent syntax. 


var adults = people
    .Where(p => p.Age >= 18)
    .ToList();

6. What Is the Difference Between First() and FirstOrDefault()?

  • First() throws an exception if no item exists.
  • FirstOrDefault() returns the default value instead.

7. What Is Exception Handling?

Exception handling allows applications to gracefully recover from runtime errors using try, catch, and finally blocks. 


try
{
    // Code
}
catch(Exception ex)
{
    Console.WriteLine(ex.Message);
}

8. What Is a Delegate?

A delegate is a type-safe reference to a method. It enables callback methods and event-driven programming.

9. What Are Events?

Events provide a mechanism for communication between objects and are commonly used in UI applications and notifications.

10. What Is async and await?

Async programming allows long-running operations to execute without blocking the current thread. 


public async Task GetDataAsync()
{
    await Task.Delay(1000);
}

11. What Is the Difference Between Thread and Task?

A Thread represents an actual operating system thread, while Task is a higher-level abstraction built on top of the thread pool.

12. What Is Dependency Injection?

Dependency Injection improves maintainability and testability by supplying dependencies from outside a class.

13. What Is Entity Framework Core?

Entity Framework Core is Microsoft's ORM for .NET applications, allowing developers to interact with databases using C# objects.

14. What Is a REST API?

A REST API exposes resources through HTTP endpoints using methods such as GET, POST, PUT, and DELETE.

15. What Is Middleware in ASP.NET Core?

Middleware components process HTTP requests and responses in the ASP.NET Core pipeline.

Common Interview Tips

  • Understand concepts instead of memorizing answers.
  • Practice writing code by hand.
  • Build small projects to gain experience.
  • Learn ASP.NET Core fundamentals.
  • Understand Entity Framework Core basics.
  • Review LINQ and asynchronous programming.

Related Tutorials

Conclusion

C# interviews often focus on programming fundamentals, object-oriented principles, collections, LINQ, asynchronous programming, and ASP.NET Core. Building a solid understanding of these topics will significantly improve your confidence and performance during technical interviews.