CodeSubmit Interview Series

The 11 Best C# Interview Questions in 2023

What are the top C# interview questions? Use these questions at your next interview to identify the right candidates for your team. Read on!

Interviewing C# developers 

C# is an open-source, general-purpose, high-level, and multi-paradigm programming language with static typing, strong typing, object-oriented, imperative, functional, generic, declarative, component-oriented, and lexically scoped disciplines. C# runs on the .NET framework. It has roots in the C family and is close to C++ and Java. 

But how do you identify the right C# developers? Here are some of the top interview questions to ask. 

Beginner C# interview questions

What are the top junior C# developer questions? In this section, we go through some top interview questions to ask at your next interview. 

1. What are the benefits of C#? 


The benefits of using C# are: 

  • Runtime environment and executable code that makes it possible to use high-level languages on different computer platforms and architectures

  • The language is easy to learn

  • C# is a general-purpose and object-oriented language

  • It’s component-oriented 

  • C# is a structured language 

  • It’s part of the .NET framework 

  • C# produces efficient programs 

2. What is an object in C#? 


C# is an object-oriented language, with classes as the foundation. Classes are templates that define what a data structure looks like and how data is stored, managed, and transferred. Classes have fields, methods, properties, and so on. 

Objects are created with class instances so that a class defines the object type. Classes can have an unlimited number of instances. 

Objects store real values, whereas classes are concepts. Any entity that can perform some work or has specific traits that are called objects. 

3. How is C# code compiled? 


There are four steps when compiling C# code. These are: 

1. Compiling source code in managed code. 

2. Clubbing newly created code with assembly code. 

3. Loading CLR (Common Language Runtime). 

4. Assembly execution through CLR. 

4. Explain garbage collection work in C#. 


Garbage collection frees up memory taken up by unwanted objects. When a class object is created, it takes up space in the heap memory and after all the actions on the object are performed, this memory space needs to be freed up. 

Garbage collection happens if the memory of the objects exceeds a pre-set threshold value, if the system has low memory, and if garbage collection is called. 

5. Explain managed and unmanaged code.


Managed code is any language written in .NET, including C#. It’s executed by CLR (Common Language Runtime). Runtime manages the whole lifecycle (memory allocation, object creation, and object disposal). 

On the other hand, unmanaged code is written outside of .NET and runs outside of CLR. For example, C or C++ are unmanaged. Developers manage execution, object creation and disposal of code. .NET enables the use of unmanaged code in managed code and the other way around.  

Advanced C# interview questions

What are the top C# interview questions? Here are some of our favorites: 

6. What is the difference between “finalize” and “dispose”? 


Finalize() is used to make objects release unmanaged resources with them without assuring garbage collection of an object. Dispose() is used in the same way while assuming garbage collection.

7. What are the different C# access modifiers? 


There are four C# modifiers. These are: 

  • Private access modifier. Private methods can only be accessed from within the class.

  • Public access modifier: A public method can be accessed from anywhere in the code. 

  • Internal access modifier: Internal methods can be accessed from the current assembly point of that class. 

  • Protected access modifier: A protected method can be accessed by members of a class and those who inherit it.

8. Explain what structs and classes have in common. How do they differ?


Classes and structures are compound data types, contain events and methods, and support interfaces. 

On the other hand, their key differences are that structs don’t support inheritance, whereas classes do. Structs value data types, classes are reference types. And structs can’t have a null reference, while references can be null in classes. 

9. Explain the difference between constant and readonly. 


Constant is a variable with a constant value except for at compile time. Constant is static and while a value needs to be assigned to it, the value can’t be changed throughout the entire program.

Readonly, again, is a keyword with value that can be changed during runtime. It can be assigned at runtime through the non-static constructor.

10. Explain extension methods. 


Extension methods, a static method of a static class, let you add methods to existing types without modifying the original type (for example, by creating a new derived type or recompiling). The “this” modifier is applied to the first parameter and the type of this parameter is extended. Extension methods are in scope when the namespace is imported to the source code with a directive. 

11. Explain how a method can be overloaded in C#? 


Overloading happens when a main() method has the same name but with different values for a different context. The step to overload methods is to change the numbers of parameters in a method, change the order of parameters, or use different data types for parameters. 

Over to you!

There you have it! Now you know what the best C# interview questions are. 

But interviews are just one part of the hiring process. You also need to assess your candidates.

That’s what CodeSubmit helps you with. Our assessment tests help you identify the best talent. 

Want to learn more?

Try CodeSubmit for free (no credit card required).