C# · Medium

Lesson 1 · On the house

Extension methods

Add methods to types you don't own with static classes and the this modifier.

Lesson 2

Iterators and yield return

Lazy sequences with yield return, yield break, and how iterator state machines run.

Lesson 3

LINQ grouping and joins

GroupBy, ToDictionary, Join, SelectMany, and Aggregate for real data shaping.

Lesson 4

Properties, indexers, and init

Auto-properties, computed getters, init-only setters, required members, and indexers.

Lesson 5

Events and multicast delegates

Declare events, subscribe with +=, raise safely with ?.Invoke, and use EventHandler<T>.

Lesson 6

async, await, and Task

Task and Task<T>, await, Task.WhenAll, and why async void is for event handlers only.

Lesson 7

IDisposable and using

Deterministic cleanup with using declarations, using blocks, and the dispose order.

Lesson 8

Generic constraints

where T : class, struct, new(), interfaces, and base types to unlock members.

Lesson 9

StringBuilder and formatting

Build strings efficiently, format numbers and dates, and use culture-invariant output.

Lesson 10

Custom exceptions and filters

Define exception types, use when filters, preserve stack traces, and finally.