vertical-slicelisted

# Vertical Slice Architecture Reference material for structuring .NET APIs by feature rather than by layer. ## Core Concept Organize code by **feature (vertical slice)**, not by technical layer (horizontal). Each slice owns everything needed for one feature: endpoint, handler, DTOs, validation. Two features never share request/response types — coupling through shared DTOs is how VSA projects collapse back into layered code. **Use when**: ≤10 aggregates, CRUD-heavy API, team prefers feature-branch isolation, or Clean Architecture feels like over-engineering. **Avoid when**: rich domain model with 10+ aggregates, complex cross-aggregate business rules, or event sourcing is on the roadmap — prefer Clean Architecture or DDD instead. See `knowledge/decisions/adr-005-multi-architecture.md`. ## Folder Structure ``` src/MyApp/ Features/ Orders/ CreateOrder/ CreateOrderEndpoint.cs # IEndpointGroup implementation CreateOrderHandler.cs # Command handler (or inline in endpoint) CreateOrderRequest.cs # Input DTO record CreateOrderResponse.cs # Output DTO record CreateOrderValidator.cs # FluentValidation validator GetOrder/ GetOrderEndpoint.cs GetOrderQuery.cs GetOrderResponse.cs CancelOrder/ CancelOrderEndpoint.cs CancelOrderCommand.cs Domain/ # Shared only if 2+ features use it Orders/ Order.cs OrderStatus.cs Infr