Learn C#

Short lessons where every snippet runs — press the button under any example, see real output. Start at the top; each lesson links to practice problems that use what you just learned.

Getting started

• Lesson 1 — Hello World
  WriteLine, comments, string interpolation, and the two shapes of a C# program (top-level statements vs class Program + Main).
• Lesson 2 — Variables & the core types
  int, double, string, bool, char — plus the three traps: integer division, overflow wrap, and floating-point surprise.
• Lesson 3 — Making decisions
  if/else chains, && and ||, switch with stacked labels, the ternary — and the golden rule that conditions are always bool.
• Lesson 4 — Loops
  for, while, do-while and foreach; the accumulator pattern, break/continue, nested loops, and which loop to reach for.
• Lesson 5 — Methods
  Parameters, return values, default arguments, out parameters and recursion — naming a recipe so you can reuse it.
• Lesson 6 — Classes & objects
  Fields, constructors, methods, auto-properties, static vs instance, and this.
• Lesson 7 — Inheritance & interfaces
  virtual/override, base constructors and calls, interfaces as contracts, is/as type tests.
• Lesson 8 — Collections
  Arrays vs List<T> vs Dictionary<K,V> — when to use each, and the tools on each.
• Lesson 9 — Exceptions
  try/catch/finally, the exception family tree, throwing your own, TryParse-vs-catch.

Where next?

The full beginner course is here. Deepen it with the error decoder (12 compiler errors, live), the articles on the classic traps, and the graded problem set.