Lesson 14: Capstone: order system architecture

This lesson practices Capstone: order system architecture at real C# application level. We start from design pain, study code, practice a small decision, predict behavior, and verify mastery.

Combine SOLID, patterns, events, and tests into one maintainable design.

Capstone: order system architecture: Combine SOLID, patterns, events, and tests into one maintainable design.
design pressure: A repeated change, duplication, or test pain that signals the model needs a better boundary.