Top C# Interview Questions and Answers (2024)

C# is a popular programming language developed by Microsoft. It is based on OOP (Object-Oriented Programming) principles. C# uses the .NET framework to build various applications, including websites, video games, Windows applications, IoT applications, and reusable libraries. This is why big companies seek skilled C# developers to add to their teams.

Here are some commonly asked C# interview questions and answers to help you start with your C# interview preparations. 

1. What are the main characteristics of C#

The main characteristics of C# are:

• It is based on OOP (Object Oriented Programming) principles
• It is a type-safe language and hence prevents type errors and improves code maintainability
• It has a unified type system, which means all types can be treated as objects
• C# has an automatic memory management that uses a garbage collector to free up the memory no longer in use
• It is interoperable with other languages and systems
• It enables you to handle runtime errors effectively with robust exception handling using ‘try’, ‘catch’, ‘finally’, and ‘throw’ keywords
• It is platform-independent

2. What is an object in C#?

An object in C# is an instance of a class that contains data and behavior as defined in the class. It is a runtime entity.

3. What are the different data types in C#?

There are three different data types in C# based on the type of data they hold - value type, reference type, and pointer.

The value datatypes store the data directly in the form of stacks. Examples of value datatypes are int, float, and char. Etc. The reference datatypes hold a reference to the variables rather than the actual data. They are stored in a heap. Reference datatypes include classes, arrays, delegates, and interfaces. The pointer datatype is used to store the address of another datatype.

4. What are jagged arrays?

A jagged array is also called an array of arrays. This means a jagged array is an array whose elements are arrays. The elements of a jagged array can have any dimensions and sizes, unlike a multidimensional array.

5. What are the different types of classes in C#?

The different types of classes in C#

Static class: these classes cannot be instantiated. This means you cannot create an object of a static class. A static class is created using the keyword ‘static’.

Abstract class: Abstract classes also cannot be instantiated and are only meant to be subclassed. The keyword ‘abstract’ is used to declare an abstract class.

Sealed class: this is the type of class that cannot be inherited.

Partial class: allows a class to be divided into multiple files.

6. What is the difference between an Array and an ArrayList in C#?

Arrays are strongly typed which means their type of element cannot be changed once declared and it stores only that datatype. On the other hand, ArrayLists are not strongly typed which means they can store elements of any datatypes.

Arrays are of fixed size once they are created. ArrayLIsts have a dynamic size and their size changes as elements are added to or removed from it. 

7. Explain the C# compilation process.

Once the source code is created, the compilation involves

1. Preprocessing - where the C# preprocesses the directives like #define, #include, etc.
2. Compilation - this is the step in the process where the source code is converted into Intermediate Language (IL).
3. Assembly - the IL code is packaged into assemblies. Assemblies can be either dynamic link libraries (DLLs) or executable files (.exe). 
4. JIT (Just-in-time) compilation - this is where the ILis converted into machine code.
5. Execution - The native machine code is executed by the CPU.

C# interview questions and answers are the perfect refresher you need to confidently face a technical C# interview. Whether you are a C# fresher or an experienced professional, brushing up on your basics and working out more technical questions will increase your chances of acing your next C# job interview.