.NET developer interview questions

.NET developer interview questions and answers

.NET interviews cover C# fundamentals, ASP.NET Core and data access with Entity Framework. These are the questions that come up most, with what each one checks.

What to revise before the interview

  • CLR, managed code and garbage collection
  • Value vs reference types, boxing and unboxing
  • Interfaces vs abstract classes
  • async/await and Tasks
  • LINQ and deferred execution
  • ASP.NET Core: middleware, dependency injection, controllers
  • Entity Framework Core: migrations, tracking, N+1 queries
  • REST API design and authentication (JWT)

  1. 1.What is the CLR?

    What they're checking
    Basic understanding of the .NET runtime.
    How to answer
    The Common Language Runtime runs .NET code: it compiles intermediate language (IL) to machine code just in time, manages memory with garbage collection and handles type safety and exceptions.

  2. 2.What is the difference between value types and reference types?

    What they're checking
    Memory and behaviour fundamentals.
    How to answer
    Value types (int, struct) hold their data directly and are copied on assignment; reference types (class, string) hold a reference to data on the heap. Mention boxing when a value type is treated as an object.

  3. 3.Interface vs abstract class - when do you use each?

    What they're checking
    Design judgement.
    How to answer
    An interface defines a contract a class can implement alongside others; an abstract class shares code and state among related classes but allows only single inheritance. Prefer interfaces for dependencies.

  4. 4.How do async and await work?

    What they're checking
    Modern C# and scalability.
    How to answer
    async marks a method that returns a Task; await pauses it until the task completes without blocking the thread, which keeps web servers responsive. Avoid .Result and .Wait(), which can deadlock.

  5. 5.What is LINQ, and what is deferred execution?

    What they're checking
    Daily C# usage and performance awareness.
    How to answer
    LINQ lets you query collections and databases with methods like Where and Select. Most queries run only when enumerated, so calling ToList() twice runs the query twice.

  6. 6.What is middleware in ASP.NET Core?

    What they're checking
    Understanding the request pipeline.
    How to answer
    Middleware are components that each handle a request and pass it on - for example logging, authentication, routing. Order matters: authentication must run before authorisation.

  7. 7.How does dependency injection work in ASP.NET Core?

    What they're checking
    Core framework knowledge.
    How to answer
    Services are registered in Program.cs with a lifetime - Singleton, Scoped (per request) or Transient - and injected through constructors. Explain why a DbContext is usually Scoped.

  8. 8.What is the N+1 problem in Entity Framework, and how do you fix it?

    What they're checking
    Real-world performance experience.
    How to answer
    Loading a list and then each item's related data runs one query plus N more. Fix it with Include() for eager loading or a projection with Select.

  9. 9.How do you secure a Web API?

    What they're checking
    Security basics for backend roles.
    How to answer
    HTTPS, authentication with JWT or OAuth, [Authorize] attributes and role or policy checks, input validation, and never returning internal errors to clients.

  10. 10.Walk me through a .NET project you worked on.

    What they're checking
    Ownership and depth.
    How to answer
    Cover the architecture (API, services, database), one decision you made and why, and a problem you solved. Keep numbers ready: users, requests or time saved.

On a live call, Cuelyte AI hears questions like these and has an answer ready in about a second, built from your resume and notes. Coding interviews: how Cuelyte AI helps

Frequently asked questions

Which .NET version should I prepare for?

Modern .NET (6 and later) with ASP.NET Core is what most new projects use. Know the differences from the older .NET Framework if your experience is with it.

Do .NET interviews include SQL?

Usually, yes - joins, indexes and stored procedures come up often, since many .NET applications use SQL Server.

Are .NET jobs common in India?

.NET is widely used in IT services and enterprise software, so roles are common, especially at services companies and their banking and healthcare clients.

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