🟢 1. C# Fundamentals (Core Language Basics)
👉 These are almost guaranteed in interviews
- What are data types in C#?
- What is the difference between int and Int32?
- What is the difference between List<T> and an array?
- What are collections in C#?
- What is boxing and unboxing in C#?
- What is the difference between a value type and a reference type?
- Explain the concept of a nullable type.
- Explain the difference between string and StringBuilder.
- What are generics in C#?
- What is a dynamic type in C#?
- What are the differences between const and readonly?
🔵 2. OOP & Design Principles
👉 Very important for “thinking ability”
- What is OOP?
- What is the difference between abstract classes and interfaces?
- What is the difference between an interface and an abstract class?
- What are design patterns? Can you name a few?
- What is SOLID?
- What is dependency injection?
🟣 3. Delegates, Events, and Advanced Language Features
👉 Tests deeper C# understanding
- What is a delegate, event, Func, Action, and Predicate Delegates?
- What are extension methods?
- What is reflection?
- Explain the concept of attributes in C#.
- Explain the role of attributes and reflection in C#.
- Explain the use of yield in C#.
🟡 4. LINQ & Data Processing
👉 VERY IMPORTANT for backend + EF Core
- What is LINQ, and how does it work?
- Deferred Execution vs. Immediate Execution?
- What are the main differences between IEnumerable and IQueryable?
- What is the difference between IEnumerable and ICollection?
🔴 5. Memory Management & Runtime
👉 Tests low-level understanding
- What is garbage collection?
- What is garbage collection and how does it work?
- What is the difference between Finalize and Dispose?
- How does the IDisposable interface work?
- What is the Common Language Runtime (CLR)?
- What is CIL (Common Intermediate Language)?
- What is the difference between managed and unmanaged code?
🟠 6. Async, Multithreading & Concurrency
👉 CRITICAL for backend roles
- Explain the async and await keywords.
- What is the purpose of the async keyword?
- How do you implement asynchronous programming in C#?
- How do you handle threading in C#?
- What is the difference between Task and Thread?
- How do you implement a multi-threaded application?
- What are the main benefits of using async/await in web applications?
- what is state machines?
🟢 7. ASP.NET Core (Web Basics)
👉 Your MAIN strength area — must be solid
- What is the ASP.NET Core pipeline?
- Explain middleware in ASP.NET Core.
- What is model binding in ASP.NET Core MVC?
- What is model validation, and how do you handle it in ASP.NET Core MVC?
- What are the different service lifetimes in ASP.NET Core (Transient, Scoped, Singleton)?
- Explain the difference between IActionResult and ActionResult.
- How do you configure and use CORS in .NET Core?
- What is Kestrel, and why is it used?
🔵 8. Security & Authentication
👉 Common real-world questions
- How do you handle security in a C# web application?
- How do you implement authentication and authorization in C#?
- How do you secure Web APIs using JWT?
- How do you implement JWT refresh tokens securely?
- How do you integrate OAuth2 and OpenID Connect?
- How do you integrate Identity Server with .NET Core?
🟣 9. Database, EF Core & Data Access
👉 VERY IMPORTANT (you use EF Core already)
- What is the role of Entity Framework Core?
- How do you perform database migrations with EF?
- Explain eager loading vs lazy loading.
- What are best practices for EF Core?
- How do you optimize SQL queries using Dapper?
- How do you create a custom collection?
🟡 10. System Design / Architecture / Tools
👉 Mid-level signals but often asked lightly
- Explain CQRS
- What is a circular reference?
- How do you implement logging in C# applications?
- How do you handle logging and error handling in production?
- How do you serialize and deserialize an object?
- What are REST vs SOAP?
- How do you optimize performance in .NET?
- How do you monitor performance and health?
☁️ 11. Cloud / Microservices / Advanced Topics
👉 Bonus but strong signal if you know
- How do you work with RabbitMQ?
- How do you integrate Docker?
- How do you work with Azure Functions?
- How do you integrate ElasticSearch?
- How do you implement API Gateway?
- How do you enable response caching?