C# Master Notes

📚 C# Master Notes

Your complete C# and .NET interview preparation guide — from fundamentals to advanced patterns.

Start Learning First Lesson
"The best way to learn is to build. The best way to build is to learn." — Every Senior Dev

What You'll Learn

🔒

Mutable vs Immutable

Understand value types, reference types, and when to use each.

📊

Records vs Classes vs Structs

Choose the right type for the right job.

❓

Nullable Reference Types

Eliminate null reference exceptions for good.

🎯

Pattern Matching

Write expressive, concise code with modern C#.

🔗

Tuples & Extensions

Return multiple values and extend types cleanly.

📦

Generics

Type-safe, reusable code with generics.

🎛️

Delegates

Pass methods as parameters with delegates and lambdas.

Why C#?

C# is one of the most versatile languages in the world — powering enterprise applications, game development (Unity), web APIs (ASP.NET), mobile apps (MAUI), and cloud services. It combines the power of C++ with the simplicity of Java, and keeps evolving with features like pattern matching, records, and source generators.

⭐ Interview Tip: C# interviews focus heavily on value vs reference types, async/await, LINQ, and garbage collection. Master these and you're 80% ready.

How to Use This Guide

  1. Start with Mutable vs Immutable — it's the foundation.
  2. Follow the sidebar order — each lesson builds on the previous.
  3. Read the One-Line Interview Answer at the end of each lesson.
  4. Practice the code examples in a .NET REPL or dotnet-script.
💡 Pro Tip: Don't just read — type every example. Muscle memory matters in interviews.