Lesson 10: Events and Observer

This lesson practices Events and Observer at real C# application level. We start from design pain, study code, practice a small decision, predict behavior, and verify mastery.

Publish events so side effects do not invade the domain model.

Events and Observer: Publish events so side effects do not invade the domain model.
design pressure: A repeated change, duplication, or test pain that signals the model needs a better boundary.