Dependency Injection

Dependency Injection

To use pipelines with Dependency Injection call AddPipeline(), or one of its overloads, when configuring the application.

Example 1

Register pipelines with DI using defaults.

services.AddPipeline();

Pipeline dependencies

Sometimes Pipelines and Pipeline middleware need access to specific container services. This can be accomplished by registering services with the PipelineContextFactory. This can be done through DI configuration, or manually through the PipelineContextFactoryProvider if you are not using DI.

Pipelines manage dependencies with a specialized container. This allows the implementor to control the services that are exposed through the pipeline. If you want to expose all application services then you can call AddPipeline and pass includeAllServices: true.

Example 2

Register pipelines with DI and provide Pipeline dependencies using the application container.

services.AddPipeline( includeAllServices: true );

Example 3

Register Pipelines with DI and provide Pipeline dependencies using a specialized container.

services.AddPipeline( (factoryServices, rootProvider) =>
{
    factoryServices.AddTransient<IThing>()
    factoryServices.ProxyService<IPrincipalProvider>( rootProvider ); // pull from root container
} );

Example 4

Register Pipeline services manually and provide Pipeline dependencies using a specialized container.

var serviceProvider = new ServiceCollection()
       .AddTransient<IPrincipalProvider>()
       .BuildServiceProvider();
   
PipelineContextFactory.CreateFactory( serviceProvider );

// get the `PipelineContextFactory` without DI
var factory = PipelineContextFactory.Instance;

Once you have registered pipeline services, custom middleware can get service instances at runtime by accessing the context.ServiceProvider property.

context.ServiceProvider.GetRequiredService<IPrincipleProvider>()

Middleware Provider

Register an IPipelineMiddlewareProvider to inject cross-cutting hooks and wraps into pipelines via DI. Commands that accept the provider can use PipelineFactory.Create to apply the middleware automatically. See Middleware for details.

services.AddSingleton<IPipelineMiddlewareProvider, MyMiddlewareProvider>();

Result Mapper

Register an IResultMapper to apply shared exception-to-HTTP-status mapping across endpoints. See the AspNetCore README for details.

services.AddSingleton<IResultMapper, ConflictResultMapper>();