Learn C# - .NET Programming

C# tutorial & compiler: coding practice, quizzes and interview questions

Learn C# from your first Console.WriteLine to ASP.NET Core, one short lesson at a time. Write code in the built-in C# code editor, run it through our online C# compiler, and practise in a hands-on lab made for this app. No IDE or SDK to install.

C# (C Sharp) is the language of .NET (dotnet): backend services, desktop apps, cloud APIs, and the scripting language of Unity. This tutorial takes you there step by step, for complete beginners and working developers alike.

WHAT YOU'LL LEARN
• The basics: variables, types, operators, strings and control flow
• Methods, arrays, collections (List, Dictionary, HashSet) and generics
• Object-oriented programming (OOP): classes, interfaces, inheritance and records
• LINQ, delegates, lambdas, events and pattern matching
• Exceptions, files, serialization and unit testing
• async/await, tasks, cancellation and parallelism
• .NET for real work: dependency injection, Entity Framework Core, ASP.NET Core minimal APIs, Blazor, SignalR and gRPC
• 93 courses and 340+ bite-sized lessons, from A1 beginner to advanced level

THE C# LAB: PRACTISE, DON'T JUST READ
• Katas: 20 coding exercises with hidden tests that turn green as you solve them
• Console Lab: programs that read input with Console.ReadLine, checked against saved inputs
• LINQ Playground: see the result after every operator, then turn the pipeline into real code and run it
• Debug Duel: a new broken program every day. Find the bug before time runs out
• Modern C# Lab: spot newer language syntax and see how the same code is written the classic way
• Async & Memory: step through the stack, the heap and threads line by line
• Code Recall: spaced-repetition cards to review what each snippet prints
• Interview Simulator: a scored mock interview with real interview questions on generics, LINQ and async

BUILD REAL PROJECTS
• 20 guided projects: temperature converter, shopping list, inventory with Dictionary, LINQ stats, generic stack, state machine, CSV parser and more
• Every step is checked by compiling and running your code
• 60 coding missions with XP to practise coding outside the lessons

AI MENTOR AND QUIZZES
• Ask the AI Mentor about a compiler error, a LINQ query or an OOP concept and get a clear answer
• A quiz after each topic, plus flashcards and a cheat sheet for quick review

COMPETE AND GET CERTIFIED
• World Coding Challenge: 3 global coding rounds every day, judged by AI, with a live leaderboard
• Certificate exam: pass it and share your certificate with a verification code
• Streaks, XP, daily reminders and progress tracking keep your practice going

HOW IT WORKS
1. Pick a course and start with a short lesson
2. Try every example in the editor and change it to see what happens
3. Lock it in with a quiz, a kata or a mission
4. Stuck? Ask the AI Mentor, then move on to the next topic

WHO IT'S FOR
• Beginners who want a serious first programming language
• Students who need extra practice and exercises
• Developers preparing for .NET and backend job interviews
• Java, Python or JavaScript developers adding C# and dotnet to their toolkit
• Future game developers getting ready for Unity

FREE TO START
Your first course is free. The daily kata and the daily Debug Duel are free, and you get one AI Mentor question a day. CoddyKit Pro unlocks every course, every lab and all missions, removes ads and lifts the daily AI Mentor limit.

The app is available in 22 languages. Download Learn C# and write your first program today.

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