93 questions in 8 topics
C# Basics Interview Questions
Types, operators, strings, nullable values and exceptions, the basics of every campus and junior round.
- What is C# and how is it related to .NET?
- What are the built-in data types in C#?
- What is the difference between
stringandStringin C#? - What do
7 / 2and7 / 2.0evaluate to in C#?
OOPs in C# Interview Questions
Classes, inheritance, polymorphism, interfaces and the keywords virtual, override, new and sealed.
- What are the four pillars of OOP, and how does C# support each?
- What is the difference between an abstract class and an interface in C#?
- How do
overrideandnewbehave when called through a base class reference? - What is the difference between method overloading and overriding?
.NET Interview Questions
How a C# program runs: the CLR, the JIT, memory, garbage collection and IDisposable.
- What is the CLR, and how does a C# program run?
- What is the difference between value types and reference types?
- How does garbage collection work in .NET?
- What is
IDisposable, and what does theusingstatement do?
C# Collections and LINQ Interview Questions
List, Dictionary, HashSet and the LINQ behavior that trips people up: deferred execution, yield, IQueryable.
- What is the difference between an array,
List<T>andArrayList? - What is the difference between
IEnumerable<T>,ICollection<T>andIList<T>? - How does
Dictionary<TKey, TValue>work internally? - What is a
HashSet<T>, and when would you use it?
C# Async and Await Interview Questions
Tasks, threads, async and await, cancellation, deadlocks and thread safety.
- What do
asyncandawaitdo in C#? - In what order does the code around an
awaitrun? - What is the difference between a
Taskand aThread? - What is the difference between
Task.WhenAll,Task.WaitAllandTask.WhenAny?
Modern C# Features Interview Questions
Records, patterns, nullable references, init and Span<T>; they need a modern SDK, so output is in comments.
- What is a record in C#, and how is it different from a class?
- What are switch expressions and pattern matching in modern C#?
- What are nullable reference types in C# 8?
- What do
initandrequireddo on properties?
Advanced C# Interview Questions
Delegates, generics, variance, dependency injection, memory leaks, LINQ performance and the ASP.NET Core pipeline.
- What is the difference between a delegate and an event in C#?
- What are generic constraints in C#? Give an example.
- What are covariance and contravariance in C# generics?
- What is the difference between
throw;andthrow ex;?
C# Coding Interview Questions
Classic coding questions solved in idiomatic C#, each linked to a problem you can submit on the Coddy judge.
- How do you reverse a string in C# without using
Array.Reverseor LINQ? - Write a C# method that checks whether a sentence is a palindrome, ignoring case and punctuation.
- How do you count how many times each character appears in a string in C#?
- How do you find duplicate values in an array in C#?
Frequently Asked Questions
How do I prepare for a C# interview?
Cover C# basics (types, strings, OOP keywords), .NET runtime topics (value and reference types, GC, IDisposable), collections and LINQ, then async and await. Practice writing small programs by hand, since most rounds include a coding question such as Two Sum. Predict each snippet's output before you run it.
What C# topics are asked to freshers?
Data types, value vs reference types, string immutability, ref and out, access modifiers, virtual and override, abstract classes vs interfaces, exception handling, and simple coding questions such as FizzBuzz. Expect at least one predict-the-output question.
What is asked in a C# interview for 5 or 10 years of experience?
Design and runtime behavior: async internals and deadlocks, thread safety, garbage collection and memory leaks, LINQ and Entity Framework performance, dependency injection lifetimes, the ASP.NET Core pipeline and modern C#. At 10 years, expect system design and how you would structure a large codebase.
Do I need data structures and algorithms for a C# developer interview?
Yes, the basics. Know Dictionary, HashSet, Stack, Queue and List and the cost of their operations; arrays, strings, hashing, two pointers and simple linked lists cover most fresher and mid-level coding rounds.
Which C# version should I know for interviews?
Know C# 7 (tuples, out var, is patterns), common in existing code, and the features up to C# 12 (.NET 8): records, switch expressions, nullable reference types, init and required, primary constructors. Naming a C# 13 or 14 addition, such as the Lock type or the field keyword, shows you keep up.
