Most Popular C# Interview Questions

Accenture, Google, Delivery Hero, and Microsoft are among the many tech companies using C#. More and more companies prefer C#, and the demand for developers with C# skills is steadily increasing.

We know the stress of facing unexpected technical questions during interviews. That is why it is useful to practice before going to a technical software interview. By reviewing the most common C# interview questions we have listed, you can prepare yourself for the challenge.

Whether you are a beginner who wants to become a C# developer or an experienced professional looking for a new job, here are the most frequently asked C# interview questions and answers.

1. What is C#?

C# (pronounced C Sharp) is a programming language developed by Microsoft for running server and embedded systems. It is one of the object-oriented programming languages designed to work within the .NET Framework environment.

C# is based on C and C++, but it also includes new features such as automatic memory management and support for the Common Language Infrastructure (CLI).

One of the key features of C# is its support for object-oriented programming (OOP). It is a flexible language used for many tasks, including Windows desktop applications, web apps, mobile apps, and games.

2. What are the main features of C#?

• Object-Oriented Programming (OOP) with classes and objects
   
• Variables and data types with a wide range of options
   
• Arrays for storing multiple variables of the same type
   
• Loops (for, while, do-while)
   
• Support for classes and objects to organize code
   
• Cross-platform compatibility with .NET, running on Windows, Linux, and macOS
   

3. What is the difference between C# and C?

C# is an object-oriented programming language, while C is procedural. The main difference is that C# supports automatic garbage collection through CLR, whereas C does not. C# is also a platform-independent language.

4. What is the difference between arrays, lists, and collections in C#?

• Arrays: Fixed size, indexed data structures.
   
• Lists: Dynamic size, indexed data structures.
   
• Collections: More advanced and customizable data structures.
   

The choice depends on the project needs.

5. What is garbage collection in C#?

Garbage collection is the process of freeing memory taken up by unused objects. It happens in three cases:

• When memory usage crosses a defined threshold
   
• When garbage collection is explicitly triggered
   
• When the system has low physical memory
   

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

CLR manages program execution for different languages, including C#. It handles memory management, garbage collection, and security.

7. What types of classes exist in C#?

• Static class
   
• Partial class
   
• Abstract class
   
• Sealed class
   

8. When and how is threading used in C#?

Threading allows multiple tasks to run at the same time in one environment. It is useful when:

• Running long operations inside an application
   
• Performing multiple tasks simultaneously to avoid time loss
   

9. What are managed and unmanaged code?

• Managed code: Runs within the .NET CLR environment with services like garbage collection and exception handling.
   
• Unmanaged code: Runs outside .NET and does not use CLR services.
   

10. What are the keywords used for error handling in C#?

• try: Marks a block where errors might occur
   
• catch: Catches and handles errors from try block
   
• finally: Always runs, whether an error occurs or not
   
• throw: Used to raise exceptions
   

11. What are accessors in C#?

Accessors control access to class properties:

• get retrieves the value
   
• set assigns a value
   

12. What are value and reference types in C#?

• Value types: Store data directly (e.g., int, bool, float, struct, enum)
   
• Reference types: Store references to memory addresses (e.g., string, object, class, array, interface, delegate)
   

13. What is a destructor in C#?

A destructor is a special method called automatically when an object’s lifetime ends. It is the opposite of a constructor and helps in memory management with the Garbage Collector.

14. What is an enum in C#?

An enum is a data type that assigns names to numeric constants, making code more readable and maintainable.

15. What are Boxing and Unboxing in C#?

• Boxing: Converting a value type to a reference type
   
• Unboxing: Converting a reference type back to a value type
   

16. What are partial classes in C#?

Partial classes allow splitting a class definition across multiple files. This is helpful for managing large and complex classes.

17. What are the data types in C#?

• Numeric types: int, long, float, double, decimal
   
• Character types: char
   

18. (continued). What are extension methods in C#?

Extension methods let you add new methods to existing classes without modifying them. They must be defined in a static class.

19. How is exception handling done in C#?

Exception handling ensures errors are managed without breaking program flow, using try-catch-finally blocks.

20. What is LINQ in C#?

LINQ (Language Integrated Query) is used to query, filter, sort, and transform data directly within C#. It works with databases, XML files, arrays, and lists.

21. What is the use of the "using" statement in C#?

The "using" statement ensures resources are disposed of properly after use.

22. Can you use "this" inside a static method?

No, "this" cannot be used in static methods because they do not belong to an instance.

23. What is the difference between ref and out parameters?

• ref: The variable must be initialized before passing.
   
• out: The variable does not need to be initialized before passing, but must be assigned inside the method.
   

Start Your C# Career

Learning C# can help you build a strong career. It is considered one of the most important programming languages to learn today.

If you are just starting, you can join C# bootcamps to build your skills. If you are an experienced developer, you can join Coderspace and find the right job opportunity for you