1. What is .NET?
.NET is a software framework developed by Microsoft that provides a controlled programming environment for building and running applications.

2. What are the key components of .NET Framework?
The key components of .NET Framework are:
– Common Language Runtime (CLR)
– Framework Class Library (FCL)
– ASP.NET
– ADO.NET

3. What is CLS?
CLS (Common Language Specification) defines a set of rules and guidelines that every language targeting .NET should follow to enable language interoperability.

4. What is CTS?
CTS (Common Type System) defines all possible data types and programming constructs supported by the .NET Framework, which ensures datatypes compatibility across different .NET languages.

5. What is the difference between value types and reference types?
Value types hold the actual data, while reference types store a reference to the memory location where the data is located.

6. What is garbage collection in .NET?
Garbage collection is a process of automatic memory management that deallocates memory occupied by objects that are no longer in use.

7. What is the difference between “StringBuilder” and “String”?
The main difference is that “StringBuilder” is mutable (can be modified), while “String” is immutable (cannot be modified).

8. What is the difference between “Finalize” and “Dispose” methods?
“Finalize” is a method called by the garbage collector to release unmanaged resources, while “Dispose” is a method called explicitly by the programmer to release these resources.

9. What are the different types of JIT compilers?
The different types of JIT compilers in .NET are:
– Pre-JIT (compiles entire code before execution)
– Econo-JIT (compiles only necessary methods immediately before execution)
– Normal-JIT (compiles methods when they are called for the first time)

10. What is an abstract class in .NET?
An abstract class is a class that cannot be instantiated and is meant to be extended by other classes. It can contain both abstract and non-abstract methods.

11. What is a sealed class in .NET?
A sealed class is a class that cannot be inherited or extended by other classes.

12. What is the purpose of using “using” keyword in C#?
The “using” keyword is used for automatic resource management. It ensures that the object is disposed of when it is no longer needed.

13. What is the difference between “ref” and “out” parameters in C#?
“ref” parameters are used to pass values both into and out of a method, while “out” parameters are used to return a value from a method.

14. What is an interface in .NET?
An interface is a contract that defines the functionality that a class must implement. It only contains the declaration of methods, properties, and events but not their implementation.

15. What is a delegate in .NET?
A delegate is a type that represents a reference to a method. It allows methods to be passed as parameters or returned as values, providing a mechanism for callbacks and event handling.

16. What is the purpose of the using statement in C#?
The using statement in C# is used for automatic disposal of resources, such as database connections, file streams, etc. It ensures that the resources are properly closed and released.

17. What is the difference between “as” and “is” operators in C#?
The “as” operator is used for casting reference types, providing null if the cast fails, while the “is” operator is used for type checking, returning a boolean indicating if the object is of the specified type.

18. What are extension methods in .NET?
Extension methods allow adding new methods to an existing type without modifying its original implementation or creating a new derived type. They are defined in a static class and used as if they were instance methods.

19. What is an anonymous type in C#?
An anonymous type is a dynamically created type that does not have a predefined name. It is typically used for temporary or one-time use and simplifies code by eliminating the need for defining custom types.

20. What is the difference between an abstract class and an interface in .NET?
An abstract class can contain both implemented and abstract methods, while an interface can only contain method signatures. A class can inherit only one abstract class, but can implement multiple interfaces.

1. What is the difference between value types and reference types in .NET?
Value types are stored in the stack memory and are copied by value, while reference types are stored in the heap memory and are copied by reference.

2. Explain the concept of boxing and unboxing in .NET.
Boxing is the process of converting a value type to a reference type. Unboxing is the opposite process of converting a reference type back to a value type.

3. What is a delegate and how is it used in .NET?
A delegate is a type that represents a method signature and allows methods to be passed as parameters to other methods. It provides a way to encapsulate a method call.

4. What are events and how do they work in .NET?
Events are a way to provide notifications to an object’s subscribers when something of interest happens. They are based on the publisher-subscriber model and use delegates to handle the event.

5. Explain the role of the Global Assembly Cache (GAC) in .NET.
The Global Assembly Cache (GAC) is a central repository for storing shared .NET assemblies. It allows multiple applications to reference and use the same version of an assembly.

6. What is the purpose of the Finalize() method in .NET?
The Finalize() method is used for garbage collection in .NET. It is called by the garbage collector before an object is reclaimed, giving the object a chance to perform any necessary cleanup.

7. How can you implement thread safety in .NET?
Thread safety can be implemented using various techniques such as locking, using thread-safe collections, using synchronization mechanisms like mutex, semaphore, etc.

8. Explain the difference between an abstract class and an interface in .NET.
An abstract class can have both implemented and abstract methods, while an interface only contains method signatures. A class can inherit multiple interfaces, but can only inherit from one abstract class.

9. What are extension methods in .NET?
Extension methods allow adding new methods to existing types without modifying their source code. They are static methods that are invoked on an instance of the extended type.

10. What is the purpose of the using statement in .NET?
The using statement is used to automatically dispose of unmanaged resources such as file handles, database connections, etc. It ensures that resources are properly cleaned up even in case of exceptions.

11. Explain the concept of generics in .NET.
Generics allow the creation of type-safe data structures and algorithms. They provide a way to define classes, structures, interfaces, and methods that can work with any data type.

12. What is the role of the AppDomain class in .NET?
The AppDomain class represents an isolated environment where applications are executed. It provides a controlled boundary for loading and executing assemblies, separating different applications from each other.

13. How can you secure sensitive information in .NET?
Sensitive information can be secured in .NET by using techniques such as encryption, hashing, secure storage, secure protocols, input validation, and ensuring proper authorization and authentication.

14. Explain the concept of asynchronous programming in .NET.
Asynchronous programming allows non-blocking execution of code, which improves the responsiveness of an application. It involves the use of asynchronous methods, tasks, and callbacks to avoid blocking the main thread.

15. What are reflection and attributes in .NET?
Reflection allows inspecting and manipulating metadata of types at runtime. Attributes are used to attach additional information to types, members, or assemblies, which can be retrieved using reflection.

16. How can you improve the performance of a .NET application?
Performance of a .NET application can be improved by optimizing algorithms and data structures, reducing unnecessary memory allocations, caching frequently accessed data, reducing database round-trips, and using efficient serialization techniques.

17. What is the role of the ASP.NET MVC framework?
ASP.NET MVC is a web application framework that follows the Model-View-Controller pattern. It provides a clean separation of concerns, promotes testability and maintainability, and allows building flexible and scalable web applications.

18. Explain the concept of dependency injection (DI) in .NET.
Dependency injection is a design pattern where dependencies are passed to a class rather than being created by the class itself. It promotes loose coupling, testability, and modularity in the code.

19. What are NuGet packages in .NET?
NuGet packages are libraries or tools that can be easily added to a .NET project. They provide reusable components and functionality, saving development time and effort.

20. How can you handle errors and exceptions in .NET?
Errors and exceptions in .NET can be handled using try-catch blocks, where the code inside the try block is executed and any exceptions are caught and handled in the catch block. Additionally, global error handling can be implemented using the Application_Error event in ASP.NET applications.