Think you’re ready for a junior .NET developer job? You might want to double-check these 50 interview questions first!

Whether you’re preparing for your first C#/.NET interview or brushing up on the basics, this guide is your cheat sheet to confidence. Based on my experience hiring and mentoring junior developers over the past 15 years, I’ve compiled a list of 50 essential questions you’re likely to encounter.

These aren’t trick questions – they’re designed to test your understanding of real-world concepts you’ll actually use.

50 Essential Interview Questions for Junior C#/.NET Developers (With Answers)

1. What is the .NET Framework?

The .NET Framework is a Microsoft platform for building applications on Windows. It includes:

• CLR (Common Language Runtime)
• A large set of class libraries (Framework Class Library – FCL)
• Support for multiple languages like C#, VB.NET, and F#

It’s primarily used for Windows applications, including desktop, web, and more.

2. What is CLR?

Common Language Runtime (CLR) is the virtual machine component of .NET. It handles:

• Memory management
• Type safety
• Exception handling
• Garbage collection
• Thread management

Think of it like the engine running your .NET application.

3. Difference between .NET Framework and .NET Core/.NET 5+?

• .NET Framework: Windows-only, legacy systems.
• .NET Core/.NET 5+: Cross-platform (Windows, Linux, macOS), open source, high performance.

Use .NET 5+ for modern development.

4. What is C#?

C# (pronounced “C-sharp”) is a modern, object-oriented programming language developed by Microsoft. It is the primary language for .NET development.

5. What is a class?

A class is a blueprint for creating objects. It defines properties (data) and methods (behavior).

public class Car {
    public string Make;
    public void Drive() {
        Console.WriteLine("Driving...");
    }
}

6. What is an object?

An object is an instance of a class.

Car myCar = new Car();
myCar.Make = "Toyota";
myCar.Drive();

7. What is inheritance?

Inheritance allows one class to inherit members (properties, methods) from another.

public class Animal {
    public void Eat() => Console.WriteLine("Eating...");
}

public class Dog : Animal {
    public void Bark() => Console.WriteLine("Barking...");
}

8. What is polymorphism?

Polymorphism allows different classes to provide different implementations for the same method.

public class Animal {
    public virtual void Speak() => Console.WriteLine("Animal speaks");
}

public class Dog : Animal {
    public override void Speak() => Console.WriteLine("Bark");
}

9. What is encapsulation?

Encapsulation means hiding internal state and requiring all interaction through public methods.

public class Account {
    private decimal balance;

    public void Deposit(decimal amount) {
        if (amount > 0) balance += amount;
    }
}

10. What is abstraction?

Abstraction hides complexity by exposing only essential features.

public abstract class Animal {
    public abstract void Speak();
}

public class Cat : Animal {
    public override void Speak() => Console.WriteLine("Meow");
}

11. What are value types and reference types?

• Value types: Store data directly (int, double, struct, bool)
• Reference types: Store reference to an object (class, string, array)

int x = 10; // Value type
string name = "Alice"; // Reference type

12. What is a constructor?

A constructor initializes a new instance of a class.

public class User {
    public string Name;

    public User(string name) {
        Name = name;
    }
}

13. What is a static class?

A static class cannot be instantiated and can contain only static members.

public static class MathHelper {
    public static int Square(int x) => x * x;
}

14. What is the difference between == and Equals()?

• == compares references for objects (unless overloaded)
• Equals() checks value equality

string a = "hello";
string b = "hello";
Console.WriteLine(a == b); // true
Console.WriteLine(a.Equals(b)); // true

15. What is a namespace?

A namespace organizes code and prevents naming conflicts.

namespace MyApp.Models {
    public class Product {}
}

16. What are access modifiers?

Control the visibility of classes and members:

• public, private, protected, internal, protected internal, private protected

17. What are properties?

Properties encapsulate a field and provide get/set access.

public class Person {
    public string Name { get; set; }
}

18. What is method overloading?

Same method name, different parameters.

public void Print(string msg) {}
public void Print(int number) {}

19. What is method overriding?

Redefining a base class method in a derived class.

public class Base {
    public virtual void Show() => Console.WriteLine("Base");
}

public class Derived : Base {
    public override void Show() => Console.WriteLine("Derived");
}

20. What are interfaces?

Contracts that define what a class must implement.

public interface IAnimal {
    void Speak();
}

public class Dog : IAnimal {
    public void Speak() => Console.WriteLine("Bark");
}

21. What is an abstract class?

A class that cannot be instantiated. It can have abstract and non-abstract members.

22. Difference between abstract class and interface?

• Abstract class: Can have implementation.
• Interface: Only method/property declarations (until default implementations in newer C#).

23. What is a delegate?

A delegate is a type that holds a reference to a method.

delegate void Greet(string name);
Greet g = msg => Console.WriteLine("Hi " + msg);
g("John");

24. What is an event?

A wrapper around delegates, used for pub-sub.

public event EventHandler SomethingHappened;

25. What is exception handling?

Mechanism to catch runtime errors and prevent crashes.

try {
    int x = 5 / 0;
} catch (DivideByZeroException ex) {
    Console.WriteLine("Cannot divide by zero");
}

26. What is try-catch-finally?

• try: Code to monitor
• catch: Handle exception
• finally: Runs always

27. What is LINQ?

Language Integrated Query – query collections using readable syntax.

var even = list.Where(x => x % 2 == 0).ToList();

28. What is async/await?

Used for asynchronous programming to avoid blocking threads.

public async Task<int> GetDataAsync() {
    await Task.Delay(1000);
    return 42;
}

29. What is a collection?

A group of objects (List, Dictionary, Array, etc.)

30. What is a List?

A generic collection that stores elements.

List<string> names = new List<string>();

31. What is a Dictionary?

A key-value pair collection.

Dictionary<int, string> users = new Dictionary<int, string>();

32. What is a foreach loop?

Iterates over a collection.

foreach (var item in list) {
    Console.WriteLine(item);
}

33. What is null?

Indicates no value or no object reference.

34. What is a nullable type?

A value type that can be null.

int? age = null;

35. What is a constructor overloading?

Multiple constructors with different parameters.

36. What is a destructor?

Used to clean up resources before an object is destroyed (rarely needed).

37. What is the difference between Stack and Heap?

• Stack: Stores value types and method calls
• Heap: Stores reference types

38. What is a sealed class?

Cannot be inherited.

public sealed class Logger {}

39. What is boxing and unboxing?

• Boxing: Converting value type to object
• Unboxing: Converting object back to value type

object obj = 123; // boxing
int x = (int)obj; // unboxing

40. What is a generic?

Allows type-safe data structures.

List<int> list = new List<int>();

41. What is dependency injection?

Injecting dependencies rather than creating inside the class. Promotes loose coupling.

42. What is MVC?

Model-View-Controller – separates logic, UI, and data.

43. What is a middleware in ASP.NET Core?

Code that handles requests/responses in a pipeline.

44. What is a view model?

A class that holds data sent between controller and view.

45. What is an attribute in C#?

Metadata for classes/methods, e.g., [Obsolete]

46. What is reflection?

Examining metadata of types at runtime.

Type t = typeof(MyClass);
MethodInfo[] methods = t.GetMethods();

47. What is a unit test?

A test to verify a specific piece of code (usually a method) works as expected.

48. What is the difference between var and dynamic?

• var: Type inferred at compile time
• dynamic: Resolved at runtime

49. What’s the difference between Task and Thread?

• Thread: Low-level, manual
• Task: High-level, integrates with async/await

50. What’s your favorite C# feature?

(Open-ended – good to show personal preference and insight)
Example:
“I love LINQ because it makes working with data collections concise and expressive.”

Conclusion: Prep Smart, Not Hard

Interview success isn’t about memorizing answers – it’s about understanding what problems each concept solves. These 50 questions aren’t just about getting hired; they’re about being ready to build real .NET applications.

So grab your IDE, test these concepts in a small project, and build confidence through practice.

If you found this helpful, let me know in the comments or check out more deep-dive posts on this blog. What’s your favorite junior-level C# interview question?