C# (pronounced “C-Sharp”) is a modern programming language developed by Microsoft. Known for its strong typing and versatility, it is widely used in software development across industries. From backend development to full-stack engineering, Unity game design to .NET roles – C# opens doors to a range of tech careers. It powers enterprise applications, cloud-based platforms, and even cross-platform games. Top companies like Microsoft, TCS, Accenture, Infosys, and Capgemini actively recruit C# professionals for high-impact roles. If you are aiming for one of these roles, brushing up on common C# interview questions is a must. This guide brings together the most asked questions along with simple answers to help you get ready for your interview.
Note – We have carefully grouped the most commonly asked C# interview questions into categories – ideal for beginners, mid-level, and experienced professionals.
C Sharp Basic Interview Questions
These are basic-level C# interview questions and answers, perfect for freshers and those building a strong foundation.
- What is C#?
C# is an object-oriented programming language developed by Microsoft. It is used to build desktop apps, web services, games, and enterprise software on the .NET platform.
- What are value types and reference types in C#?
Value types hold data directly. Examples include int, bool, and struct. Reference types store a reference to the data’s memory location. These include class, interface, and string.
- How does C# differ from C++ and Java?
C# is simpler than C++ and safer due to automatic memory management. Unlike Java, C# supports pointers (in unsafe code) and has better integration with Windows and .NET.
- What is the purpose of the using statement?
It helps manage resources like file streams or database connections. It disposes objects once they go out of scope.
- Explain the concept of boxing and unboxing in C#.
Boxing converts a value type to an object. Unboxing retrieves the value type from the object. It’s common when working with collections like ArrayList in older code.
- What is the difference between == and .Equals()?
== checks if two references or values are the same, depending on the type. .Equals() checks if the content is equal. It can be overridden in custom classes.
- How does C# handle memory management?
C# uses a garbage collector. It automatically frees unused memory. I don’t need to delete objects manually, which reduces memory-related bugs.
Note – Beginner-level interview questions about C# often include topics like data types, loops, conditionals, OOP basics, and syntax.
C Sharp Interview Questions for Freshers
This section covers C Sharp interview questions and answers for freshers, commonly asked in entry-level technical interviews.
- How is C# different from the C programming language?
C is procedural and low-level, while C# is high-level and object-oriented. C# supports garbage collection, type safety, and is better suited for modern application development.
- What is a namespace in C# and why is it used?
A namespace groups related classes, interfaces, and methods. It prevents naming conflicts and organizes code better.
- Describe the structure of a basic C# program.
It starts with using directives, followed by a namespace, a class, and a Main() method. Code runs from Main().
- What are access modifiers in C#?
They control visibility of classes and members. Common ones are public, private, protected, and internal.
- How is an interface different from an abstract class?
An interface only contains declarations. An abstract class can have both declarations and defined methods. A class can implement multiple interfaces but inherit only one class.
- What is the role of the CLR in .NET?
The CLR (Common Language Runtime) runs C# code, manages memory, handles exceptions, and enforces security.
Note – C# interview questions and answers for freshers often focus on basic syntax, OOP principles, data types, andsimple problem-solving.
C# Interview Questions for Experienced
Here is a list of commonly asked C Sharp interview questions and answers for experienced professionals.
C# Interview Questions for 2 Year Experienced
- What are delegates and how are they used?
Delegates are object-oriented function pointers. They let you pass methods as parameters, supporting event handling and callbacks. Action, Func, and custom delegates are commonly used.
- How do you handle exceptions in a layered architecture?
I handle exceptions at each layer and pass meaningful messages up. In the data layer, I log errors and avoid exposing technical details to the UI layer.
- What is the difference between const and readonly?
const values are set at compile time and must be primitive or string types. readonly values are assigned at runtime, usually in the constructor.
- When would you use a struct instead of a class?
I use struct for small data models that are immutable and value-based, like points or coordinates.
C Sharp Interview Questions for 3 Years Experienced
- What is dependency injection and why is it useful?
It is a design pattern where dependencies are passed in instead of being created inside the class. This makes the code easier to test and maintain.
- How do you implement method overloading and overriding in C#?
Overloading means defining multiple methods with the same name but different parameters. Overriding uses the override keyword to change base class behavior in a derived class.
- Explain the role of LINQ in C#.
LINQ simplifies data querying. I use it to filter, sort, and join data collections directly in C#, without writing separate loops.
C# Interview Questions for 5 Years Experienced
- How does garbage collection work in C#?
Garbage collection automatically frees memory for unreferenced objects. It runs in the background and uses generations (0, 1, 2) to manage memory efficiently.
- What are extension methods and when should they be used?
Extension methods let me add functionality to existing types without modifying them. I use them to keep code cleaner and avoid utility classes.
- How do you secure sensitive data in a C# application?
I use encryption (e.g., AES), hashing for passwords, and never store secrets in plain text. I also use secure communication (HTTPS) and validate all inputs.
C# Interview Questions for 10 Years Experienced
These are common C# .NET interview questions for 10 years’ experience, often asked in senior-level technical interviews.
- How would you architect a large-scale C# application?
I start by breaking it into layers – UI, business logic, data, and services. I prefer microservices or modular monoliths depending on the use case. I use SOLID principles, apply patterns like CQRS or Mediator, and containerize services when needed.
- What performance tuning techniques have you applied in C# projects?
I have used async calls to avoid blocking threads, optimized LINQ queries, reduced memory allocation, and minimized boxing. I also profile using tools like dotTrace or PerfView.
- How do you handle thread safety in enterprise-level applications?
I use locking (lock, Monitor, SemaphoreSlim) when accessing shared resources. For collections, I prefer ConcurrentDictionary or BlockingCollection.
- Describe a time you refactored legacy C# code to improve maintainability.
In one project, I inherited tightly coupled, repetitive logic. I broke it into services, used dependency injection, and added unit tests. It became easier to extend, and onboarding new devs got faster.
C# Advanced Interview Questions
Now, let’s go through some frequently asked advanced-level C Sharp questions and answers.
- What is covariance and contravariance in C#?
Covariance allows a method to return a more derived type than declared. Contravariance lets a method accept less derived parameters. These apply mostly to generics and delegates.
- How do you implement custom collections?
I create a class that implements IEnumerable<T> or ICollection<T>. This gives control over how data is stored and iterated.
- What is a memory leak in managed code and how can you avoid it?
It happens when objects remain in memory due to lingering references. I avoid it by unsubscribing events and disposing resources properly.
- Explain the differences between Task, Thread, and async.
A Thread is a low-level unit of execution. Task is a higher-level abstraction used with async methods. async marks methods that return Task or Task<T>.
C# Scenario Based Interview Questions
Here is a list of common scenario-based C# interview questions for experienced professionals.
- How would you debug a slow-loading C# application?
I would start by profiling the application to check CPU and memory usage, identify slow database queries, and inspect LINQ performance. I’d also review logs for patterns, check for synchronous I/O, and validate startup configurations.
- How would you design a logging system in a C# web app?
I would use ILogger with a provider like Serilog or NLog. Logs would be structured and sent to files, databases, or services like Seq or ELK. I’d include request IDs to trace user sessions clearly.
- What steps would you take to prevent SQL injection in C#?
I always use parameterized queries or LINQ with Entity Framework to avoid injecting raw SQL. I also validate inputs, restrict database permissions, and log access patterns to detect abnormal or suspicious query behavior.
C# Technical Interview Questions
Now, let’s cover some important technical C Sharp interview questions and their answers.
- Explain how the async and await keywords work together.
async marks a method that contains await. await pauses execution until the awaited task finishes, keeping UI responsive.
- What are sealed classes and why are they used?
A sealed class can’t be inherited. I use it when I want to prevent further extension or for performance optimization.
- How do you use IEnumerable and IQueryable differently?
IEnumerable executes queries in memory. IQueryable builds database queries. I use IQueryable for LINQ to SQL.
- What is reflection in C# and where would you use it?
Reflection inspects assemblies, types, or members at runtime. I use it for plugins, custom serialization, or testing tools.
C# Developer Interview Questions
Fun Fact – Over 27.1% of developers worldwide use C#. This makes it one of the top 10 most-used programming languages today.
Here are some of the most commonly asked C# interview questions for senior developer roles.
- What tools do you use for code analysis in C#?
I regularly use SonarQube for continuous inspection, ReSharper for refactoring and code quality checks, and Visual Studio’s built-in analyzers to detect issues like dead code, high complexity, and poor naming conventions.
- How do you handle version control in a team project?
We use Git with a structured workflow like GitFlow or trunk-based development. Each feature is built on a separate branch, merged via pull requests, and reviewed to catch bugs and maintain consistent code quality.
- Describe how you manage API versioning in a C# backend.
I use URL or header-based versioning with attributes like [ApiVersion] in ASP.NET. Each version has separate controllers or routes, which helps support older clients without breaking newer implementations.
- How do you use configuration management in .NET applications?
I use appsettings.json for base configs, IOptions for binding, and separate environment files for staging and production. Secrets are handled via secure stores or environment variables to avoid hardcoding sensitive data.
C# Coding Interview Questions
This section features important C# programming interview questions that test real-world coding skills and problem-solving abilities.
- Write a C# program to reverse a string without using built-in methods.
You might be asked to write such string programs in C# for interviews.
string Reverse(string input)
{
char[] result = new char[input.Length];
for (int i = 0; i < input.Length; i++)
{
result[i] = input[input.Length – 1 – i];
}
return new string(result);
}
- Write a program to find duplicates in an integer array.
void FindDuplicates(int[] arr)
{
var seen = new HashSet<int>();
foreach (int num in arr)
{
if (seen.Contains(num))
Console.WriteLine(“Duplicate: ” + num);
else
seen.Add(num);
}
}
- How would you implement a custom sorting logic using IComparer?
class DescComparer : IComparer<int>
{
public int Compare(int x, int y)
{
return y.CompareTo(x); // Descending order
}
}
// Usage
var numbers = new List<int> { 5, 2, 9 };
numbers.Sort(new DescComparer());
- Write a program to check if a number is prime.
bool IsPrime(int number)
{
if (number < 2) return false;
for (int i = 2; i <= Math.Sqrt(number); i++)
{
if (number % i == 0) return false;
}
return true;
}
C# Programs for Interview
Here are some commonly asked C Sharp interview programs to test your coding logic.
- Program to print Fibonacci series using recursion.
int Fibonacci(int n)
{
if (n <= 1) return n;
return Fibonacci(n – 1) + Fibonacci(n – 2);
}
- Program to swap two numbers without using a temporary variable.
void Swap(ref int a, ref int b)
{
a = a + b;
b = a – b;
a = a – b;
}
- Program to find the factorial of a number.
int Factorial(int n)
{
if (n == 0) return 1;
return n * Factorial(n – 1);
}
- Program to check for a palindrome string.
bool IsPalindrome(string s)
{
int start = 0, end = s.Length – 1;
while (start < end)
{
if (s[start] != s[end]) return false;
start++; end–;
}
return true;
}
C# MCQ Questions
- What is the default value of a bool in C#?
A. true
B. false
C. 0
D. null
Answer: B. false
- Which keyword is used to define a constant value?
A. final
B. constant
C. const
D. static
Answer: C. const
- What does the static keyword mean?
A. Method runs only once
B. Variable is shared across all instances
C. Object can’t be created
D. Method is private
Answer: B. Variable is shared across all instances
- Which of these is not a value type?
A. int
B. float
C. string
D. bool
Answer: C. string
- What is the size of int in C#?
A. 2 bytes
B. 4 bytes
C. 8 bytes
D. Depends on system
Answer: B. 4 bytes
Other Important C# Interview Questions
These are some other important C# interview questions covering advanced topics like collections, Web API, exception handling, design patterns, inheritance, and practical programming tasks.
C# and .NET Interview Questions
This section includes essential C# .NET interview questions commonly asked for roles involving application development, backend systems, and enterprise solutions.
- What is the difference between .NET Core and .NET Framework?
- How does C# interact with the .NET runtime?
- What are the different GC generations in .NET and how do they improve memory management?
- What is the Global Assembly Cache (GAC)?
Note – These C Sharp .NET interview questions are great for brushing up before technical rounds.
C# Automation Testing Interview Questions
These are frequently asked C# interview questions for automation tester roles.
- How is C# used with Selenium for UI testing?
- What are the advantages of using NUnit with C#?
- How do you handle waits in automated test scripts?
- How do you manage test data in C# automation frameworks?
C# Generics Interview Questions
This section covers commonly asked generics interview questions in C#.
- What are generics in C# and why are they useful?
- How do you create a generic method?
- Can you restrict types in a generic class?
- What’s the difference between generic and non-generic collections?
C# Multithreading Interview Questions
These are common C# thread interview questions asked in technical interviews to test knowledge of multithreading concepts.
- What is a thread in C#?
- How do you create and start a thread?
- How do you avoid race conditions?
- What is the role of lock in C#?
Async Await C# Interview Questions
These are common async and await in C# interview questions asked to evaluate your understanding of asynchronous programming and task-based execution.
- What is asynchronous programming in C#?
- How does async differ from await?
- How do you handle exceptions in async methods?
- What’s the difference between Task, Task<T>, and void in async methods?
WPF Interview Questions C# Corner
These are common C Sharp Corner interview questions related to WPF, often asked to test UI development skills using C# and XAML.
- What is data binding in WPF?
- How does the MVVM pattern work in WPF?
- What is the difference between a Canvas and a Grid?
- How do you apply styles and themes in WPF?
C# Design Patterns Interview Questions
- What is the Singleton pattern and how is it implemented in C#?
- What is the Factory pattern used for?
- When would you use the Observer pattern?
- What are some real-life examples of design patterns in .NET projects?
C# Web API Interview Questions
- What is the purpose of a Web API?
- How do you secure a C# Web API?
- What is the difference between GET and POST in API calls?
- How do you return custom responses from a controller?
C# Collection Interview Questions
- What is the difference between List, Array, and Dictionary?
- How do you choose the right collection type in C#?
- What is the use of HashSet?
- What is the time complexity of accessing elements in a List?
Entity Framework Interview Questions C#
- What is the difference between EF Core and EF6?
- How do you implement migrations in EF?
- What is lazy loading in EF?
- How do you write raw SQL queries in Entity Framework?
C# Exception Handling Interview Questions
- What is the difference between throw and throw ex?
- What is the role of finally block?
- How do you create a custom exception?
- What are best practices for exception handling?
Abstract Class C# Interview Questions
- What is an abstract class in C#?
- How does it differ from an interface?
- Can an abstract class have constructors?
- When should you use an abstract class?
Array Program in C# for Interview
- Write a program to find the second-largest number in an array.
- Write a program to merge two arrays.
- Write a program to find the common elements in two arrays.
- Write a program to rotate an array.
Inheritance C# Interview Questions
- What is inheritance in C#?
- How do you override a base class method?
- Can a class inherit multiple classes in C#?
- How do you call a base class constructor?
Tips to Prepare for Your C# Interview
A little focused preparation goes a long way when you want to give a strong C# interview performance.
- Brush up on core C# concepts like OOP, data types, and access modifiers.
- Write and test small programs regularly.
- Practice explaining code out loud.
- Review commonly asked questions and real-world scenarios.
- Learn basic .NET concepts if you haven’t already.
- Keep answers short and honest.
- Stay calm and think before you speak.
Wrapping Up
These 50+ C# interview questions and answers cover the kind of topics that actually come up in real interviews. Go through them carefully, try writing a few answers on your own, and think about how you would explain each concept out loud.
Looking to apply what you have prepared? Start your job search on Hirist – a platform built for IT professionals. Find C# job roles that match your skills and experience, all in one place.
FAQs
What is the average salary for a C# developer in India?
According to AmbitionBox, C# developers in India typically earn between ₹2 LPA to ₹11.5 LPA depending on experience, location, and skills. Senior roles, especially in product-based companies, can go beyond ₹20 LPA.
Which top IT companies in India hire C# developers?
Popular companies hiring for C# roles include –
- TCS
- Infosys
- Accenture
- Cognizant
- HCL Tech
- Wipro
- Capgemini
- Microsoft India
- Zensar
- Mphasis
Many product companies and startups also use C# for backend and desktop development.
What is the best way to answer C# interview questions?
Don’t just repeat definitions. Use real examples, keep your answers short and clear, and talk through your thought process. If you are not sure, be honest and explain how you would find the solution.
Where can I find a reliable collection of C# interview questions on GitHub?
You can search GitHub for repositories like “CSharp-Interview-Questions” or “.NET-Interview-Prep”. Many developers share real interview questions, sample answers, and practical coding tasks there.
What are some commonly asked C# question answer sets for interviews?
Most interview sets include a mix of core concepts, OOP, collections, and .NET framework topics. Here are a few examples –
- What is the difference between ref and out in C#?
- How does garbage collection work?
- What is the difference between an abstract class and an interface?
- Explain the use of async and await.
What are some C# problem-solving questions asked in technical interviews?
These questions usually test logic, syntax, and your ability to write clean code. Common ones include –
- Reverse a string without using built-in functions.
- Find duplicates in an array.
- Count character frequency in a string.
- Write Fibonacci series using recursion.
- Remove duplicates from a list.
Should I learn .NET along with C# for better job opportunities?
Yes. Most C# roles involve working on .NET frameworks like ASP.NET or .NET Core. Knowing both gives you more options, especially for web and enterprise application jobs.
