Top C# Interview Questions and Answers

Here are top C# interview questions,

1. What is C#?

C# is a modern, general-purpose programming language developed by Microsoft. It is part of the .NET framework and is primarily used for developing Windows applications and web services.

 

2. What is the difference between "ref" and "out" parameters in C#?

"ref" parameters require the variable to be initialized before passing it to a method, while "out" parameters do not require initialization and the method must assign a value to it before returning.

 

3. What is a nullable type in C#?

A nullable type allows a variable to hold either a valid value or a null value. It is denoted by appending a question mark (?) to the type declaration.

 

4. What are the access modifiers available in C#?

C# provides five access modifiers: public, private, protected, internal, and protected internal. These modifiers control the visibility and accessibility of classes, methods, and variables.

 

5. What is the difference between a class and an object in C#?

A class is a blueprint or template for creating objects, while an object is an instance of a class. Classes define the properties and behavior of objects.

 

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

An abstract class can have both abstract and non-abstract methods, while an interface can only have abstract methods. A class can inherit from a single abstract class but can implement multiple interfaces.

 

7. What is the difference between a struct and a class in C#?

A struct is a value type and is stored on the stack, while a class is a reference type and is stored on the heap. Structs are typically used for small, lightweight objects.

 

8. What is boxing and unboxing in C#?

Boxing is the process of converting a value type to an object reference, while unboxing is the process of converting an object reference back to a value type. Boxing and unboxing have performance implications.

 

9. What is the difference between a shallow copy and a deep copy in C#?

A shallow copy creates a new object but references the same memory locations for internal members, while a deep copy creates a new object and copies the values of all internal members to new memory locations.

 

10. What is the purpose of the "using" statement in C#?

The "using" statement is used to automatically dispose of unmanaged resources such as files, database connections, etc. It ensures that resources are properly released even if an exception occurs.

 

11. What is the difference between a StringBuilder and a string in C#?

A StringBuilder is mutable, meaning it can be modified, while a string is immutable and cannot be changed once created. StringBuilder is more efficient when concatenating or modifying strings frequently.

 

12. How does exception handling work in C#?

Exception handling in C# is done using try-catch-finally blocks. Code that may throw an exception is enclosed in a try block, and if an exception occurs, it is caught in a catch block. The finally block is used to execute cleanup code.

 

13. What is the purpose of the "var" keyword in C#?

The "var" keyword allows the compiler to infer the type of a variable based on the value assigned to it. It is mainly used for brevity and does not mean that the variable is dynamically typed.

 

14. What is the difference between "readonly" and "const" in C#?

"readonly" variables can be assigned a value either at the time of declaration or in the constructor, and their values cannot be changed afterward. "const" variables are compile-time constants and their values cannot be changed.

 

15. What is the purpose of the "yield" keyword in C#?

The "yield" keyword is used in iterator methods to create an iterator block. It allows the method to return a sequence of values one at a time without having to create a collection explicitly.

 

16. What is the difference between synchronous and asynchronous programming in C#?

Synchronous programming executes code sequentially, blocking until each operation completes. Asynchronous programming allows multiple operations to be executed concurrently, improving performance and responsiveness.

 

17. What is the role of the "async" and "await" keywords in C#?

The "async" keyword is used to define an asynchronous method, while the "await" keyword is used within an asynchronous method to wait for the completion of an asynchronous operation without blocking the thread.

 

18. How do you implement inheritance in C#?

Inheritance in C# is implemented using the ":" symbol. A derived class inherits the members of the base class and can extend or override them as needed.

 

19. What is a delegate in C#?

A delegate is a type that represents a method signature. It allows methods to be passed as parameters or stored in variables, enabling callback mechanisms and event handling.

 

20. How does garbage collection work in C#?

Garbage collection in C# automatically manages the memory used by objects. The garbage collector periodically checks for unreferenced objects and frees the memory occupied by them. Developers do not have to manually free memory.

Above are few top C# interview questions. Remember to prepare and expand on these answers.

Good luck with your interview!  👍