README.md

Order Processing Example

Every other project in this repo shows one pattern in isolation. This one shows three of them working together in a single, small scenario: placing an order.

• Builder (OrderBuilder) assembles an Order from a fluent chain of calls instead of a constructor with a long parameter list.
• Strategy (IDiscountStrategy) picks how the subtotal turns into a total — NoDiscount, PercentageDiscount, or FixedAmountDiscount — without OrderProcessor knowing which one it got.
• Observer (IOrderObserver) lets OrderProcessor notify an open-ended list of reactions — email, inventory, audit log — when an order is placed, without knowing what any of them actually do.

None of the three patterns depend on each other here: swap the discount strategy, add or remove observers, or change how the order is built, and the other two are unaffected. That's the point — each one solves a separate concern, and the example composes cleanly because they don't leak into each other.

Run

dotnet run --project OrderProcessingExample