C#
Full course · 21 lessonsC# is Microsofts flagship language for the .NET ecosystem. It powers Windows applications, game development (Unity), cloud services on Azure, and cross-platform apps. These are the definitive free resources — vetted, current, and complete.
Getting Started with C# and the .NET CLI
Install the .NET SDK, understand dotnet CLI (new/build/run), project structure, and write Hello World.
Variables and Built-in Types
Value vs reference types, var inference, built-in numeric types, and default values.
Operators and Expressions
Arithmetic, comparison, logical, bitwise operators; precedence and null-coalescing.
Control Flow and Switch Expressions
if/else, switch statements and expressions, loops, and jump statements.
Methods and Parameters
Method signatures, ref/out/in params, params arrays, named and optional arguments.
Arrays, Lists, and Collections
Arrays, List<T>, Dictionary<TKey,TValue>, Queue, Stack; collection initializers.
Strings and String Interpolation
String immutability, interpolation, StringBuilder, and common string methods.
Classes and Objects
Class declarations, constructors, this, static members, and object initializers.
Properties, Indexers, and Fields
Auto-properties, get/set accessors, computed properties, and indexers.
Inheritance and Polymorphism
Base and derived classes, virtual/override, protected members, sealed.
Interfaces and Abstract Classes
Interface contracts, abstract classes, multiple interface implementation.
Generics
Generic types and methods, constraints, and covariance/contravariance.
LINQ: Language Integrated Query
Query and method syntax, deferred execution, standard query operators.
Delegates, Events, and Lambdas
Delegate types, multicast delegates, events, lambda expressions, Func/Action.
Exceptions and Error Handling
try/catch/finally, exception filters, custom exceptions, throw expressions.
Async Programming: async/await and Tasks
Task-based async model, await semantics, parallel tasks, error handling.
Files and Streams
System.IO, File/FileInfo, StreamReader/Writer, binary streams, using disposal.
Iterators, IEnumerable, and Span<T>
yield return, IEnumerable/IEnumerator, lazy evaluation, Span and Memory.
Nullable Types and Pattern Matching
Nullable value types, nullable reference types, is patterns, switch patterns.
Records, Structs, and Tuples
Record types, with-expressions, tuples, deconstruction, structs as value types.
Advanced: Reflection, Attributes, and Memory
Reflection, custom attributes, unsafe code, garbage collection, performance.
Free Books
Official C# Documentation Guide
The modern living reference book built into the Microsoft ecosystem covering everything from basics to advanced features like records and pattern matching.
C# Programming Yellow Book (Rob Miles)
A legendary friendly introductory textbook used in university CS courses. Free PDF download covering programming from first principles.
Official Documentation
C# Language Reference
The definitive source for C# syntax rules, compiler options, and language specifications from Microsoft.
.NET API Browser
The complete reference library for all managed Microsoft namespaces, classes, methods, and structures.
Microsoft Learn C# Path
Interactive step-by-step browser modules taking you from absolute beginner to building functional apps.
Interactive Courses
Video Courses
C# Full Course for Beginners (freeCodeCamp)
A comprehensive multi-hour video tutorial covering core programming principles to advanced features like LINQ and async/await.
C# for Beginners (Microsoft Developer)
Hosted by Scott Hanselman and experts from the .NET team. The official Microsoft beginner series.
Practice & Challenges
Exercism — C# Track
178 free hands-on exercises with automated CLI tests and human mentors who review your idiomatic C# code.
Codewars — C# Katas
Community-driven code challenges ranging from beginner to advanced in C#.
LeetCode — C# Support
Practice algorithms and data structures using C# for interview preparation.
Reference & Cheatsheets
News & Updates
Community
Reddit r/csharp
The premier active community for .NET and C# discussions, career advice, and project showcases.
C# Discord Server
A massive real-time chat community for troubleshooting code and discussing software design.
Stack Overflow — C# Tag
The ultimate archive for troubleshooting bugs, syntax errors, and best practices in C#.