Update 2021 - C# Interview Questions and Answers

By Andrea

Last updated on Aug 11 2021

Update 2021 - C# Interview Questions and Answers

Most Commonly Asked C# Interview Questions and Answers 2021


Introduction to C#


C# (aka C sharp) is an object-oriented programming language which is used widely by developers to carry out multiple tasks and accomplishes numerous goals. Basically, there are many types of object-oriented programming languages such as C++, Python, Java. And these programming languages are developed for a specific framework. Likewise, the C# is also designed and developed for a specific framework, i.e. .NET. The .NET framework is a brainchild of Microsoft. And it provides a massive platform to create applications, declarations, and commands for applications and so on. 


When the C# language was introduced in the market, it was named as COOL which stood for C-like Object-Oriented Language. But Microsoft was unable to carry forward this name as there were some issues regarding trademark law. Then they decided to change its name from COOL to C#. At that time, Java became the thought leader of the programming industry. This provoked other companies to create their own best framework. 


And this is the reason why Microsoft developed its own framework .NET and created a new OOP programming language to rival Java. And Microsoft diverted the market demands towards its C# language. The C# came out to perform faster and better than Java. And the developers across the globe popularly used to build applications meticulously. 


The C# got global acceptance and appreciation for not only performing better, but it was easy to use too. It was easy enough to be used just by having some knowledge about codes. Further with practice, the users could develop muscle memory to use C#. The C# can be used for web development, games, mobile apps, applications for windows and other such programs. With such features, the usage of C# has surged, and demands for professionals who could use it precisely has increased two folds. In this article, we have organized and listed all the important interview questions that are asked most frequently. In here, we have categorized questions amongst three distinct levels:

  1. Beginner Level C# Interview Questions
  2. Intermediate Level C# Interview Questions
  3. Advanced Level C# Interview Questions

We have done so to help you learn about the C# interview questions easily in a systematic way.


Beginner Level C# Interview Questions


Q1. List some of the features with the definition of C#.

A programming language is used to write software for a website, a desktop application or a mobile application. All of these types of software is built using a programming language.

 In C# we have .Net framework that has virtual machines like Common Language Runtime or CLR & Base class Libraries. Any application code is compiled and run into the windows; .Net framework comes into action by executing it. We use Visual studio .Net in the Microsoft word to write the codes. 


This allows us what type of application we are going to build and what programming language we are going to use. There is plenty of programming language that the .Net support but C# is easy to learn, easy to work with and doesn’t sacrifice power and control.


C# is known as an object-oriented programming language that means we build and model our application by looking at its blueprint. These blueprints are classes that help us to model our application. Every time a user uses this application, then one part of these blueprint gets turned in to an actual object in memory to work with.


Q2. Mention the different types of comments in C#?

To be specific comments are the message you put on your code or you want to deactivate some lines of code and see how it works without them or describe what some of your code is trying to perform.

comment line uses double slash followed by the comment. It breaks up the code and makes it look a little nicer if it is an advanced code than its wise to put in a couple of comment just to explain what is going on.




// These two lines change the colour of the text.

Comment Blocks must start with a “/” followed by an “*” & it must finish with an “*” and a “/”. You can have as many lines in between them as you like. And then you can add a Multi-line comment to describe things that are going on.



/* Comment line

*Comment block

*comment web report




Comment web report: You can do it before the static void main, or you can do it for the class program. You do three “///” & you will find XML to pop up where you write the summary about the void main in here.


/// This is comment web report, looks great!



Q3. What are some of the IDE’s provided by Microsoft for C# development?

IDE or integrated development environment is a piece of software that helps us to write codes. IDE makes developing applications program easier. It acts as a text editor, debugger, and compiler all in one. There are many different types of IDEs; some common IDEs are Visual Studio, Xcode, Android Studio, Pycharm, eclipse, sublime, Adam, to name a few.




> if (programmer)

> {

> use This = True

> }


Q4. Chart out the process of code compilation in C#.

We have the language independency when we are working with .Net framework, the complete compilation process for any particular language in .Net framework we can classify the compilation process into two parts. The first step involves compiling of the language by the compiler and then redirected to a intermediate language. While in the second phase the compilation is done by the JIT or Just-In-Time.

code compilation in C sharp


Q5. Differentiate between managed and unmanaged code?

The code that executes with the CLR instead of operating system is called as a Managed code. In the managed code the runtime will provide services like garbage collector, type checking & exception handling. The code is compiled by the language compiler into Intermediate language.

While a code that does not execute under CLR and is directly executes in the operating system is called as unmanaged code. It does not provide services like garbage collector & type checking, it should be taken care by the programmer itself. He should write the code to deal locate the memory. Here code will be compiled into native code.


Intermediate Level C# Interview Questions


Q1. Differentiate Finally Block and Finalize Block.

At the end of performing the try and catch blocks, the final block is declared. The finally block basically utilized to handle the exception. When some sort of exception is found in the block of code while performing the block, normally these block codes contain cleaner codes, to clean the exception.

When the exception is found, then the next should be garbage collection. At these types of circumstances, the Finalize method is called for the cleaning operation to run successfully.


Q2. What do you know about managed and unmanaged codes?

The managed code is that type of code which is performed or executed by Common Language Run-time. This indicates that the application codes hinge on the .NET platform. At the same time, the unmanaged code can be defined as the codes that are performed by a run-time application which doesn’t belong to the .NET framework. In those cases, the memory, security and execution of unmanaged codes totally depend on that different run-time application. 


Q3. Define an Object in C#

The Object can be referred to as an instance of any class. In order to access the methods of a class, one has to make use of objects. To create or generate an object, the developers should use a separate and fresh keyword. The creation of an object takes place in the memory location of a class. The memory location of that class comprises of the required data of methods, behaviour and variables of the class.


Q4. Define class

In general, a class can be defined as an outline of an object. The class decides the basic functions and abilities that an object should possess. As the class is an object’s blueprint, an object can be called as an instance of the class. It is the class that helps the developers to produce an object. However, in C#, the class is basically termed as a keyword of class or class keyword.


Q5. What is an abstract class in C#?

An abstract class can be defined as a type of class which consists of a particular technique, and it is written with “Abstract” keyword. As the abstract class has a specific approach, an object cannot be instantiated from this class.


Q6. How will you define sealed classes in C#?

A sealed class is a type of class which is created in such a way that it cannot be inherited by C#. Unlike the abstract class, a sealed class can be instantiated, but it cannot be inherited. The main purpose of the sealed class is to limit the inheritance of class.


Q7. What do you mean by partial class in C#?

The partial class is a type of class that divides the definition of a single class into multiple classes. This segregation of single class definition can be carried out by means of the same source codes or various different source codes. It is possible to create one class definition in numerous files, but that is accumulated as a single class at the run-time application. And then an instance or object of that class is produced. And with the help of that object, the user can easily enter into all the methods of the class from various source files. The partial class is depicted by the keyword “Partial”.


Q8. What are the fundamental OOP concepts in C#?

One can list down four fundamental Object-Oriented Programs concept, and those are:

  • Inheritance

When the characteristic feature is transferred to create another class without any modification, then such activity is called inheritance. In this concept, the class from which its features are transferred is called as Base class or Parent Class. And the class in which those features are “transferred on” is called as Child Class. 

  • Polymorphism 

Polymorphism in the programming world can be defined as the ability of an object that permits the object to transform into different states.

  • Encapsulation

The encapsulation is a process in which the multiple data are bound together in one class. And the user cannot get access into that data directly, but it should be done by prefixing an underscore.

  • Abstraction

This is a process in which the developers will have the command to show a specific detail, and they can hide data from the users which are not important from the user’s point of view. This process is necessary to resolve the complicated issue by designing and creating classes which are suitable to solve specific issues. Further, for an abstract class, an object cannot be instantiated.


Q9. How would you inherit a class into another class in C#?

Various platforms use various codes to inherit any class. In case of C# colon is used to operate inheritance.


Q10. What is Method Overloading in C#? Elucidate.

The method overloading is a common process that is carried out in C# to create a number of methods which will contain the same name and specific signatures. This process is carried out with the same class. On completion of the method overloading process, the compiler initiates operations to invoke specific actions on the basis of method overloading.


Q11. Distinguish between Method Overloading and Method Overriding in C#?

Method Overriding is a process in which the basic definition of a derived class is changed. And eventually, this process alters the method behaviour of the derived class. 

Whereas method overloading can be defined as a process in which multiple methods are generated that comprise the same name and different signatures under the same class.


Q12. What is Stream Reader and Stream Writer class in C#?

There are certain data that cannot be read casually, in order to read such data a specific class used which are Stream Reader and Stream Writer. These are the two classes which originate from namespace.System.IO. And these classes are used to read charact90 and write Reader Based data correspondingly.


Q13. Define Interface.

The interface can be defined as a class which comprises of property declaration, attributes declaration and event declaration.


Q14. How will you differentiate Virtual Method and Abstract Method?

The virtual method can be defined as a method which comes along with a default implementation. And it allows the developers to override it by simply using the keyword override.


The abstract method, on the other hand, is a method that is present in the abstract class. And it is compulsory for the derived class to use the abstract class. Further, it basically doesn’t come along with an implementation whatsoever. And there is no necessity to override the abstract method.


Q15. What do you mean by Namespace in C#?

Namespaces can be defined as a command that can be utilized to organize and manage projects of huge codes. The namespace used in the C#, but the most prominently used namespace in C# is the “System”. It is permissible for a user to generate their specific namespaces and to use one namespace on another namespace is called Nesting.


Q16. How will you define the Using Statement in C#?

The “using” can be defined as a keyword that is executed to signify a specific Namespace.


Q17. What is Jagged Array in C#?

In C# there is a term which called a Jagegd Array. It generally means an “array of arrays”. Its components are arrays, and these components may possess various dimensions. This reflects the possibility length-wise difference of array index.


Advanced Level C# Interview Questions


Q1. Define Delegates?

A delegate is a type safe function pointer. It holds the reference of method & then calls the method for execution. In C# we can call a method in two types:

  • Static
  • Delegate

There are three steps to call a method by using a delegate:

  1. Defining a delegate by [] delegate void|type( [])
  2. Instantiating the delegate- it is the process of creating the instance of the delegate and in the process you have to pass the method name as a parameter to the delegate constructors.

  AddDelegate ad = new AddDelegate(p.AddNums);

  SayDelegate sd = new SayDelegate(Program.SayHello);

  1. Now call the delegate by passing required parameter values, so that internally the method which is bound with the delegate gets executed.


Q2. Define Generics?

Generic are introduced in C# 2.0 it allow us to design classes and methods decoupled from the data types. These reusable codes classes decrease the code redundancy, the name space, parameterized type are used to create generic collection.

Q3. Explain Deadlock with an example?

Let say we have two threads and two resources as depicted below in the figure.

deadlock in c sharp

Thread 1 has already exclusively acquired a lock on Resource1 and wants to achieve a lock of Resource 2. At the same time Thread 2 has already acquired a lock on Resource 2 & wants to acquire a lock on a Resource1. Two threads never give up their locks hence a deadlock is formed. A deadlock is a situation in which 2 or more transaction are waiting for one another to give up lock. Here T1 is waiting for T2 & vice versa.  Lock(X) are exclusive locks that can both read and write. Whereas Lock(S) or shared lock can only read operations. There are three necessary conditions in Deadlock:

  • Hold & Wait
  • Mutual Exclusion
  • No Preemption
  • Circular weight.



Q4. What are Spawn Threads with thread pool?

A thread is a part of CPU or a multiple CPUs that is captured & used solely for process. We could say that at any given time multiple threads run multiple processes. To see how threads work, take a look at this example. Thread pool is nothing but a collection of threads. Here collection means preconfigured thread to serve incoming task-Async. A task function runs asynchronously is created first & helps to increase application’s responsiveness. For example Google search example.

Public Static void ThreadCounter(i);


for  ( ( int i = 0; I < 10;i++)



                        Thread. Sleep(0);



Q5. Illustrate Thread and explain multithreading?

To understand the perspective of multithreading let’s look into the concept of multi-tasking. OS to run these applications run simultaneously will make use of a process. A process is a part of the OS responsible to execute the application. Each process runs one application. The windows OS also has background processes & these are windows services. 

Operating system:

- Process

- Thread

Thread is unit which executes the logic into every application. Every application has by default one thread to execute to the logic called as “Main thread”. So, every program is by default is single threaded model.

Using systems;

Class ThreadDemo


 Static void Main()






Compiling this code will run this logic:

Using systems;

Using system.Threading;

Class ThreadDemo


 Static void Main()


   Thread t = Thread.CurrentThread;

t.Name = “Main Thread”;

 Console.WriteLine(“Current executing thread is : “+ Thread.CurrentThread.Name);



Here “t” refers to the executing thread.


Thread allows us to have multiple path of execution going through our codes simultaneously. In a single threaded model actions are executed one after another or sequential in nature, but if, suppose the time lingers then we will get glitches like downtime in response.


To overcome this particular problem we can use the concept of multi-threading.

Multi-threading contains more than one thread to execute. Meaning in one thread we will have multiple process where each method execute simultaneously. Here OS shares the time period for each thread to execute. In other words, our programs going to be able to branch off so that the application is going to be doing multiple things at the same time. You probably have one CPU with a few cores in it but we will have ten or more threads going at the same time. The CPU switches between these threads giving little slices of time to each one and by cycling through them it’s going to give us the appearance that more than one thing is going on at the same time.



So these are the most important questions that are asked in the C# interview, and you will have to be thorough with all these questions to pass in your interview.

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About the Author

Sprintzeal   Andrea

Technical Content Writer with experience in creating engaging content in IT field

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