18Software Engineering · Interview Prep · Free
.NET Developer interview questions — and how to answer them.
These are the questions .NET Developer candidates are most likely to face, from openers to the hard ones — each with a note on what a strong answer covers. Want more, tuned to your level? Use the free generator below.
What interviewers look for in a .NET Developer
- Concrete examples of systems you've built, with the trade-offs you weighed
- How you debug — the process, not just the fix
- Collaboration signals: code review, disagreements, mentoring
Likely .NET Developer interview questions
1. Can you walk us through your experience with .NET development? What versions have you worked with?
Mention specific projects, frameworks (.NET Framework vs .NET Core vs .NET 5+), and your progression over time.
2. Tell me about a time you had to debug a difficult issue in production. How did you approach it?
Describe your systematic debugging process, tools used (logging, profilers, debuggers), and the resolution outcome.
3. What's the difference between `async/await` and traditional threading in C#? When would you use each?
Explain async/await benefits (non-blocking, scalability), threading use cases, and pitfalls like deadlocks.
4. Describe your experience with Entity Framework or another ORM. Have you encountered any performance issues?
Discuss lazy loading vs eager loading, N+1 problems, query optimization, and when raw SQL is appropriate.
5. How do you approach writing unit tests in C#? What testing framework do you prefer and why?
Cover test structure (Arrange-Act-Assert), mocking/dependency injection, coverage goals, and xUnit/NUnit/MSTest preferences.
6. Tell me about your experience with RESTful API design. How do you handle versioning and error responses?
Discuss HTTP status codes, versioning strategies (URL vs headers), consistent error formatting, and documentation.
7. What design patterns have you used in .NET applications? Give a concrete example.
Name specific patterns (Dependency Injection, Repository, Factory, Singleton) with real scenarios and trade-offs.
8. How would you implement dependency injection in a .NET application without using a third-party container?
Explain constructor injection, service locator anti-pattern awareness, and benefits of DI for testability.
9. Describe your experience with SQL Server or another database. How do you optimize database queries?
Discuss indexing, execution plans, query analysis tools, N+1 prevention, and connection pooling.
10. How do you handle concurrency issues in .NET? Explain locking, immutability, or concurrent collections.
Cover race conditions, lock statements, ReaderWriterLockSlim, ConcurrentDictionary, and thread-safety patterns.
11. Walk us through your experience with CI/CD pipelines for .NET. What tools have you used?
Mention Azure DevOps, GitHub Actions, Jenkins, build automation, automated testing stages, and deployment strategies.
12. Design a scalable .NET microservices architecture for a high-traffic e-commerce platform. What technologies and patterns would you use?
Address service separation, async messaging (queues), API gateways, caching strategies, database per service, monitoring, and resilience patterns.
Want to practice answering live with scored feedback? Try the Mock Interview Coach. Applying too? See a .NET Developer cover letter example.
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