Top necessary 20 questions with answer to prepare for interview - C#

 Author - Amatya Agyey

Tech Lead - Motherson

1. What is the difference between a class and a struct in C#? Answer: A class is a reference type, while a struct is a value type. Objects of a class are allocated on the heap, whereas struct instances are allocated on the stack.

2. Explain the difference between a shallow copy and a deep copy. Answer: A shallow copy creates a new reference to the same memory location, while a deep copy creates a new copy of the entire object and its referenced objects.

3. What are the access modifiers available in C#? Answer: C# provides five access modifiers: public, private, protected, internal, and protected internal.

4. How do you handle exceptions in C#? Answer: Exceptions can be handled using try-catch-finally blocks. The try block contains the code that may throw an exception, and the catch block catches and handles the exception. The finally block is used to execute code that should always run, regardless of whether an exception occurred or not.

5. What is the purpose of the 'using' statement in C#? Answer: The 'using' statement is used to ensure that IDisposable objects are properly disposed of when they are no longer needed. It automatically calls the Dispose method on the object, even if an exception occurs.

6. Explain the difference between 'const' and 'readonly' variables in C#. Answer: 'const' variables are compile-time constants and their values cannot be changed. 'readonly' variables are assigned at runtime and can be different for different instances of the same type, but once assigned, their values cannot be changed.

7. What is the difference between 'IEnumerable' and 'IQueryable' in C#? Answer: 'IEnumerable' is used to represent a collection of objects that can be enumerated, while 'IQueryable' represents a queryable collection of objects that can be queried using LINQ.

8. What are delegates in C#? Answer: Delegates are type-safe function pointers that allow methods to be passed as parameters or assigned to variables. They are often used for event handling and asynchronous programming.

9. Explain the concept of polymorphism in C#. Answer: Polymorphism allows objects of different types to be treated as objects of the same base type. It enables the use of a single interface to represent multiple implementations.

10. What is the purpose of the 'yield' keyword in C#? Answer: The 'yield' keyword is used in iterator methods to simplify the implementation of custom iterators. It allows the method to return a sequence of values without requiring the entire sequence to be generated upfront.

11. How do you implement multithreading in C#? Answer: Multithreading can be implemented in C# using the Thread class, the ThreadPool, or the Task Parallel Library (TPL). The TPL provides higher-level abstractions for working with tasks and parallelism.

12. Explain the concept of extension methods in C#. Answer: Extension methods allow adding new methods to existing types without modifying their original definitions. They are a convenient way to add functionality to classes or interfaces that you don't have control over.

13. What is the purpose of the 'async' and 'await' keywords in C#? Answer: The 'async' and 'await' keywords are used in asynchronous programming to simplify the implementation of asynchronous code. 'async' marks a method as asynchronous, and 'await' is used to asynchronously wait for a task to complete.

14. How do you implement a singleton pattern in C#? Answer: The singleton pattern ensures that a class has only one instance and provides a global point of access to it. It is typically implemented by making the constructor private and providing a static method to access the single instance.

15. Explain the concept of dependency injection (DI) in C#. Answer: Dependency injection is a design pattern where the dependencies of a class are provided from the outside rather than being created internally. It promotes loose coupling and makes the code more testable and maintainable.

16. What are attributes in C#? Answer: Attributes provide a way to associate metadata with types, methods, properties, and other program elements. They can be used for a variety of purposes, such as adding information for reflection or customizing code generation.

17. How do you work with databases in C#? Answer: C# provides various ways to work with databases, such as using ADO.NET, Entity Framework, or other ORM frameworks. ADO.NET allows direct interaction with databases using classes like SqlConnection, SqlCommand, and SqlDataReader.

18. What is the purpose of the 'volatile' keyword in C#? Answer: The 'volatile' keyword is used to indicate that a variable can be accessed by multiple threads and its value may change unexpectedly. It ensures that reads and writes to the variable are atomic and not optimized by the compiler or CPU.

19. How do you work with files and directories in C#? Answer: C# provides classes like File and Directory in the System.IO namespace to work with files and directories. These classes offer methods for creating, deleting, moving, and manipulating files and directories.

20. Explain the concept of reflection in C#. Answer: Reflection allows examining and manipulating the metadata of types at runtime. It provides the ability to dynamically load assemblies, inspect types, invoke methods, and access properties and fields