Top .NET Interview Questions & Answers – Advanced Edition

• If you’re preparing for senior or mid-level .NET interviews, expect questions beyond syntax. Here are some advanced Q&A you should be ready for:

Questions & Answers

• Que1: What is the difference between IEnumerable, IQueryable, and List in .NET?
• Ans: IEnumerable works in-memory and is best for simple iteration.
• Ans: IQueryable allows deferred execution and runs queries on the database side.
• Ans: List is a concrete in-memory collection with indexing and modification support.

• Que2: Explain the difference between Task, Thread, and ValueTask.
• Ans: Thread: OS-level execution unit.
• Ans: Task: Higher-level abstraction over threads for async operations.
• Ans: ValueTask: Optimized for scenarios where the result may already be available, reducing allocations.

• Que3: How does Dependency Injection (DI) work in .NET Core?
• Ans: .NET Core has a built-in IoC container. Services are registered with lifetimes:
• Ans: Singleton (one instance per application), Scoped (one instance per request)
• Ans: Transient (new instance every time)
• Ans: This promotes loose coupling and testability.

• Que4: What’s the difference between struct and class in C#?
• Ans: struct is a value type, stored on the stack, lightweight, and doesn’t support inheritance.
• Ans: class is a reference type, stored on the heap, supports inheritance, and is more flexible.

• Que5: How do you improve performance in an ASP.NET Core application?
• Ans: Use caching (in-memory, distributed, response caching)
• Ans: Use async/await properly
• Ans: Optimize EF Core queries (projection, AsNoTracking())
• Ans: Profile & monitor with Application Insights