Top C# Coding Interview Questions and Answers You Need to Prepare

Released in 2002 by Microsoft, C# is a programming language widely used in web development. Owing to its significance in the tech field, C# coding interview questions are given a lot of importance during technical interviews. 

Because there are so many questions to sort through, practicing the most important C# coding interview questions can be difficult for freshers and experienced professionals. In this article, we'll look at the top questions you should practice to ace the C# coding interview.

If you’re a software engineer, coding engineer, software developer, engineering manager, or tech lead preparing for tech interviews, check out our technical interview checklist, interview questions page, and salary negotiation e-book to get interview-ready! 

Having trained over 9,000 software engineers, we know what it takes to crack the most challenging tech interviews. Since 2014, Interview Kickstart alums have landed lucrative offers from FAANG and Tier-1 tech companies, with an average salary hike of 49%. The highest-ever offer received by an IK alum is a whopping $933,000!

At IK, you get the unique opportunity to learn from expert instructors who are hiring managers and tech leads at Google, Facebook, Apple, and other top Silicon Valley tech companies. Our reviews will tell you how we’ve shaped the careers of thousands of professionals aspiring to take their careers to new heights. 

Want to nail your next tech interview? Sign up for our FREE Webinar.

In this article, we’ll be covering the following topics:

• What is C#, and What are its Features?
• Most PopularC# Coding Interview Questions and Answers
• Sample C# Coding Interview Questions for Practice
• FAQs on C# Coding Interview Questions

What is C# and What are its Features?

Pronounced ‘see sharp,’ C# is an object-oriented programming (OOP) language. It was released in 2002 by Microsoft and standardized by ISO and ECMA to be used on the .NET platform. The latest version of the language is C# 6.0. 

The primary features of C# are:

• It’s a simple, modern, purely object-oriented programming language.
• It includes a feature known as versioning that helps create new versions of module work using the existing version.
• It’s several times faster than BASIC

Most Popular C# Coding Interview Questions and Answers

To prepare you for your technical interview, here are some basic and advanced C# coding interview questions and answers to get you started: 

Q1. Name the different types of classes in C#.

The different classes in C# are:

1. Partial class - It lets members be divided or shared with multiple .cs files and is denoted by the keyword Partial. 
2. Sealed class - This class cannot be inherited, and to access members of a sealed class, you need to create the object of the class. It’s denoted by the keyword Sealed. 
3. Abstract class: It’s a class where the object can’t be instantiated and can only be inherited. Its keyword is abstract.
4. Static class - This class doesn’t allow inheritance, and the members are also static. It’s denoted by the keyword static.
   

(This is a very popular C# coding interview question, just a heads-up.)

Q2. Why is the virtual keyword used in code?

The virtual keyword is used for determining a class to specify that the methods and properties of that class can be overridden in derived classes. 

Q3. Why should you use finally block in C#?

The finally block will be carried out irrespective of exception. So when an exception occurs while executing the code in the try block, the control is given back to catch block, and then finally block is executed. 

Q4. List the advantages of C# as a programming language.

Some major advantages of using C# are:

• C# can be integrated with other technologies, languages, frameworks (such as .NET), or applications.
• It has a secure recovery system that ensures there aren’t any memory leaks.
• The library consists of an array of impressive tools that make implementation convenient.
  

Q5. Differentiate between method overriding and method overloading?

Method overriding: Also known as RunTime Polymorphism, Dynamic Polymorphism, or Late Binding, this process is responsible for creating a method in the derived class using the same signature and name in the base class.

Method overloading: Also known as Early Binding, Compile Time Polymorphism, or Static Binding, it creates two or more functions (or methods) using the same name but different parameters in the same class. 

Q6. What’s the difference between dispose and finalize methods in C#?

The difference is:

Dispose () - It is used to release unmanaged resources (such as files, database connections, etc.) when asked for specifically. 

Finalize () - It releases the unmanaged resources present on the code prior to garbage collection.

Q7. Give examples of some exceptions in C#. 

Some exceptions in C# are:

• ArgumentNullException - It occurs when a null reference is passed to a method that doesn’t consider it as a valid argument.
• NullReferenceException - It shows an error when the user tries to gain access to a member on a type whose value is null.
• DivideByZeroException - It takes place when the user tries to divide an integral or decimal value by zero.
  

Q8. What is object pool in C#?

The object pool is responsible for tracking the objects used in the code when a request is made for a new object to reduce the object creation overhead.

Q9. How does the Sentinel Search work? 

The purpose of linear search is to compare the search item with elements present in the list one at a time with the help of a loop and stop the moment the first copy of the search element in the list is obtained. If you consider the worst case in which the search element doesn’t exist in the list of size N, then the Simple Linear Search will consider a total of 2N+1 comparisons.

Coming to Sentinel Linear Search, the idea behind it is to cut down the number of comparisons needed to find an element in a list. In this, the last element of the list is replaced with the search element itself, and a while loop is run to determine if a copy of the search element in the list exists. The loop is quit as soon as the search element is found. It reduces one comparison in each repetition.  

(Another important C# coding interview question, so prepare accordingly.)

Q10. How to check if the two Strings (words) are Anagrams?

If two words contain the same number of characters and have the same number of characters, they’re anagrams. There are two solutions you can mention:

1. You can sort the characters using the lexicographic order and find out whether all the characters in one string are equal to the other string and are in the same order. If you sort either array, the solution will be - 0(n log n).
   

2. You can also go for the Hashmap approach in which key - letter and value - frequency of letter,

• For the first string, populate the hashmap 0(n)
• For the second string, decrement the count and then remove the element from hashmap 0(n)
• Only if the hashmap is empty are the strings an anagram; otherwise, they aren’t
  

Q11. How do you differentiate between Struct and a Class in C#? 

Although class and struct both are user-defined data types, they do have some major differences:

Class

• It is a reference type in C# and inherits from the system.object type 
• Usually used for large amounts of data
• Can be inherited to other class
• Can be the abstract type 
  

Struct

• It is a value type in C# and inherits from the system.object Type
• Used for smaller amounts of data
• Can’t be inherited to other type
• Can’t be abstract
  

Q12. How can a class be prevented from overriding in C#?

A class won’t be overridden in C# if the sealed keyword is used. 

Q13. Is there a distinction between throw and throw ex?

The difference between throw and throw ex is as follows:

• In throw ex, that thrown expectation becomes the ‘original’ one. All previous stack trace won’t be there.
• In throw, the exception just goes down the line, and you’ll get the full stack trace.
  

Q14. Explain the difference between Equality Operator (==) and Equals() Method in C#?

== Operator (usually means the same as ReferenceEquals, it can be overridden) is used to compare the reference identity. On the other hand, the Equals() (virtual Equals () )method compares whether two objects are equivalent.  

Q15. What’s the use of Null Coalescing Operator (??) in C#?

Known as the null-coalescing operator, the ?? operator defines a default value for nullable value types or reference types. It is responsible for returning the left-hand operand if the operand is not null. Else, it returns the right operand. 

Extra C# Coding Interview Questions

When you’re preparing for the technical interview, ensure that you prepare the following C# coding interview questions as well. These will come in handy to experienced professionals as well as freshers.

Q1. Which C# structure would you use to get the fastest large objects manipulation?

Q2. Which C# features do you like the most and why?

Q3. How, according to you, can a great # code be written?

Q4. Explain the difference between interface and abstract class?

Q5. Will you be able to write the FizzBuzz program in C# now?

Q6. What is LINQ in C#? Have you ever used it?

Q7. Define Dynamic Dispatch. 

Q8. What makes your code really object-oriented?

Q9. How to avoid the NULL trap?

Q10. List the fundamental principles of OO programming?

Q11. Name three ways to pass parameters to a method in C#.

Q12. Give some features of generics in C#.

Q13. What are delegates and their types in C#?

Q14. Compare ‘string’ and ‘StringBuilder’ in C#. 

Q15. In C#, what’s the differentiating factor between an abstract class and an interface?

FAQs About C# Coding Interview Questions

Q1. What interview are questions asked in C#?

Some C# coding interview questions are: Give examples of the different types of comments in C#. Differentiate between public, static, and void. What are Jagged Arrays?

Q2. Which topics are asked in C# coding interview questions?

Some important topics when preparing for C# interview questions are: CLR, CLS, CTS, Classes & Objects, and OOPs.

Q3. How do you differentiate between C# and C?

One of the most important differences between C and C# is that while C language can be executed cross-platform, C# (pronounced C sharp) requires a .NET framework to execute the language.

Q4. What is the extension method in C# interview questions?

The extension method is a static method of a static class and can be used with the help of the instance method syntax. Extension methods are useful in adding new behaviors to an existing type without altering anything.

Q5. How do you prepare for C# coding interview questions?

Keep your C# basics on point and practice mock interviews. You can even take part in coding competitions to improve your speed and accuracy.

Gear Up for Your Next Technical Interview

If you’re having trouble preparing for C# coding interview questions or any other type of technical interview, register for our free webinar to get expert guidance from FAANG+ industry experts on nailing technical interviews at top tech companies.

With our team of expert instructors who are hiring managers at FAANG+ companies, we’ve trained over 9,000 engineers to land multiple offers at the biggest tech companies and know what it takes to nail tough technical interviews.