Today we're going to talk about some of the most common interview questions you might be asked in a C# interview. This article is based on my own experience, as well as insights shared with me by other developers.

Good news first! Most of the time, interviews for C# developer positions don’t include any LeetCode questions at all. This might be related to the types of companies hiring for these roles, but generally, you can skip LeetCode if you're aiming for a C# position. Instead, focus on design pattern questions and the SOLID principles.

A little bit of background: before I became a developer myself, I worked with and coached other devs on their interview preparation. Over time, I compiled a solid list of questions you’ll want to review before your own interview. Fasten your seatbelt—let’s dive in!

List of C# questions

✅ Latest version of C#?

✅ What is the difference between value type and reference type?

✅ What is the difference between abstract classes and interfaces?

✅ Can we write method body inside an interface?

✅ How will you prevent a class from being inherited by its child classes?

✅ Overloading (static pm) and Overriding(runtime pm, dynamic) in OOP?

✅ Why we use access modifiers; tell about public and private, protected, internal?

✅ Which part manages memory in CLR automatically?

✅ Explain JIT Compiler?

✅ What is the difference between managed and unmanaged code?

✅ Is it possible for managed code to access unmanaged code? ( (P/Invoke))

✅ Explain LINQ and its basic syntax. Give an example?

✅ Exception Handling in C#?

✅ Explain generics?

✅ What is the difference between an array and a list?

✅ Reflection in C# (to get type-related info at runtime)

✅ Explain Collections (arrays, lists, dictionaries, queues, and stacks)

ASP.NET

✅ Difference between ASP.NET Web Forms and ASP.NET MVC.

✅ ASP.NET Core vs ASP.NET Framework.

MVC Pattern (Model-View-Controller)

✅ Understanding the MVC design pattern and how it’s implemented in ASP.NET Core.

✅ Creating controllers, views, and models in ASP.NET Core.

✅ Routing in ASP.NET Core.

Web API Development

✅ Create RESTful APIs using ASP.NET Core Web API.

✅ Understand HTTP verbs: GET, POST, PUT, DELETE, PATCH.

✅ How to create CRUD operations in Web API.

✅ Swagger for API documentation.

Dependency Injection (DI)

✅ What is DI and why it’s important?

✅ How to configure services and inject dependencies in ASP.NET Core.

Authentication and Authorization

✅ Work with Identity for user authentication and authorization.

✅ Understand JWT tokens, OAuth, and cookie-based authentication.

Middleware

✅ What is middleware in ASP.NET Core and how does it work?

✅ Write custom middleware.

Model Binding and Validation

✅ Model binding in Web API and MVC controllers.

✅ Data annotations for validation in MVC models.

State Management in Web Applications

✅ Understand cookies, sessions, and query strings in ASP.NET.

Design Patterns

✅ When to use and how to implement the Singleton pattern in C#.

✅ Understand the Factory Method and how it’s used to create objects.

✅ How to implement the Repository pattern for data access.

✅ Understanding the Observer pattern for event-driven systems.

I hope you find this list helpful! I definitely recommend making sure you can clearly explain what dependency injection and OOP are — many developers struggle to explain these concepts properly.

In my upcoming articles, I plan to dive deeper into these two topics.

For now, good luck and happy coding! 🙌