.NET Architecture

Requirement An application MUST use Domain, Application.Abstractions, Application, Infrastructure, and WebApi as its five baseline projects.

Rationale Application.Abstractions holds the contracts that more than one module names: the pipeline's own positions, the cross-module ports, the transport-neutral failures, and the published integration events. It references Domain and the required LiteBus module abstractions, and nothing else. No type in it can name a use case, a handler, or a module.

That refusal is the reason it is a project rather than a folder. A folder inside Application cannot decline what a developer puts in it, and the folder that tries becomes the place every unplaced type goes.

An implementation never belongs there. The project name states the test, and a type that cannot pass it belongs to a module under litespec/backend/architecture#place-a-type-at-the-lowest-folder-that-holds-its-consumers.

AppHost and ServiceDefaults support local hosting and diagnostics. They are hosts, not application layers.

This realizes litespec/backend/architecture#use-five-application-parts in the dotnet stack.

Example

apps/api/src/{ProjectName}.Domain/
apps/api/src/{ProjectName}.Application.Abstractions/
apps/api/src/{ProjectName}.Application/
apps/api/src/{ProjectName}.Infrastructure/
apps/api/src/{ProjectName}.WebApi/

Requirement An application MUST place commands, queries, results, validators, handlers, reactions, and module-owned ports in one Application project, and cross-module contracts in Application.Abstractions.

Rationale Separate Write, Read, Contracts, and event-handler assemblies are outside this stack. The separation this stack keeps is the one Fowler describes as CQRS, which separates the command and query models rather than the assemblies holding them. Splitting assemblies buys a deployment boundary the stack does not use, and costs a project reference that every use case has to cross.

This realizes litespec/backend/architecture#keep-one-application-part in the dotnet stack.

Requirement A handler, validator, definition, persistence implementation, or endpoint implementation MUST be declared internal sealed.

Rationale Messages, results, assembly markers, and ports stay public only when another project uses them. Assembly scanning is not a reason to widen visibility.

This realizes litespec/backend/architecture#keep-implementation-types-hidden in the dotnet stack.