dependency-injection-patterns

Group related dependency injection registrations into cohesive Add* extension methods that return IServiceCollection. This modular architecture prevents a sprawling Program.cs and enables reusable configuration across both production and test environments.

Yes, you can reuse production dependency injection registrations in tests by composing production DI once and overriding only test-specific parts. This test-time DI reuse is enabled through hierarchical composition of Add* extension methods.

The best way to layer dependency injection is through hierarchical composition of Add* extension methods. You compose domain, infrastructure, and API registrations hierarchically, allowing configuration-aware options and a modular architecture across services and repositories.

Yes, this dependency injection pattern supports configuration-aware options and is fully applicable to library design. It fulfills functional requirements for extension-based registrations that return IServiceCollection, allowing seamless integration of services and integrations.

You should reconsider using extension methods for modular architecture in dependency injection if your application lacks complex service registrations or test-time DI reuse requirements. Simple startup composition may not benefit from the added abstraction of hierarchical Add* extensions.