.NET Developer interview questions typically focus on the .NET framework, C# language, ASP.NET, MVC, web services, and related technologies. Here are 25 common questions with answers to help you prepare for your .NET Developer interview.

Q1. What is the .NET Framework?

The .NET Framework is a software development platform developed by Microsoft that supports building and running applications on Windows. It includes a large class library and runtime called CLR.

Q2. What is the Common Language Runtime (CLR)?

CLR is the execution engine of .NET Framework that manages memory, thread execution, code safety verification, and other system services.

Q3. What are assemblies in .NET?

Assemblies are compiled code libraries used for deployment, versioning, and security in .NET. They can be DLL or EXE files containing metadata and intermediate language code.

Q4. What is the difference between managed and unmanaged code?

Managed code runs under the control of CLR, benefiting from services like garbage collection, while unmanaged code runs directly on the OS outside CLR control.

Q5. What is the Global Assembly Cache (GAC)?

The GAC is a machine-wide repository used to store shared assemblies accessible by multiple applications.

Q6. Explain the difference between value types and reference types in C#.

Value types hold data directly and are stored in the stack; reference types store references to data objects stored in the heap.

Q7. What is boxing and unboxing?

Boxing is converting a value type to an object or interface type; unboxing extracts the value type from the object.

Q8. What is the difference between an interface and an abstract class?

Interfaces define a contract with no implementation, whereas abstract classes can have implementations and maintain state.

Q9. What is ASP.NET MVC?

ASP.NET MVC is a web application framework that implements the Model-View-Controller pattern, promoting separation of concerns.

Q10. What are the different types of caching in ASP.NET?

Output caching, data caching, and application caching.

Q11. What is a delegate in C#?

A delegate is a type-safe function pointer that holds references to methods with a specific signature.

Q12. What are events in C#?

Events provide a way for a class to notify clients when something happens, using delegates under the hood.

Q13. What is LINQ?

LINQ (Language Integrated Query) allows querying collections in a concise and readable syntax directly within C#.

Q14. What is Entity Framework?

Entity Framework is an ORM (Object Relational Mapper) that enables .NET developers to work with databases using .NET objects.

Q15. How does garbage collection work in .NET?

Garbage collection automatically frees memory occupied by objects that are no longer referenced by the application.

Q16. What is the difference between early binding and late binding?

Early binding occurs at compile time with type checking; late binding happens at runtime, usually via reflection.

Q17. Explain the difference between Task and Thread in .NET.

A Thread is a low-level concept for concurrent execution, whereas Task is a higher-level abstraction for asynchronous programming.

Q18. What is async and await in C#?

async and await keywords simplify asynchronous programming by allowing writing non-blocking code that looks synchronous.

Q19. What are Web API and WCF?

Web API is a framework for building RESTful services, while WCF (Windows Communication Foundation) supports SOAP and other communication protocols.

Q20. What is Model Binding in ASP.NET MVC?

Model Binding maps data from HTTP requests to action method parameters in controllers.

Q21. What is the purpose of the ViewBag and ViewData in MVC?

They are used to pass data from controllers to views; ViewBag is dynamic, ViewData is a dictionary.

Q22. What is dependency injection?

Dependency Injection is a design pattern that allows decoupling the creation of dependent objects from their behavior.

Q23. How do you handle exceptions in .NET?

Using try-catch-finally blocks to catch and handle exceptions gracefully.

Q24. What is the difference between synchronous and asynchronous controllers?

Synchronous controllers block the thread until the operation completes; asynchronous controllers free the thread to handle other requests while waiting.

Q25. How do you secure an ASP.NET application?

Using authentication, authorization, SSL, input validation, and anti-forgery tokens to prevent attacks.