Dotnet核心方法注入控制器方法

Question

Lets say i have the following controller in dotnet core:

[Route("api/v1/[controller]")]
public class ValuesController : Controller
{
    private readonly IHandler<ValuesRequest, ValuesResponse> _valueHandler;
    private readonly IHandler<ValuesIdRequest, ValuesIdResponse> _valueIdHandler;

    public ValuesController(IHandler<ValuesRequest, ValuesResponse> valueHandler, 
                            IHandler<ValuesIdRequest, ValuesIdResponse> valueIdHandler)
    {
        _valueHandler = valueHandler;
        _valueIdHandler = valueIdHandler;
    }

    [HttpGet]
    public ValuesResponse Get(ValuesRequest request)
    {
        return _valueHandler.Handle(request);
    }

    [HttpGet("{id}")]
    public ValuesIdResponse Get(ValuesIdRequest request)
    {
        return _valueIdHandler.Handle(request);
    }
}

As you can see in the code above, I'm using dependency injection though the constructor. However, I was thinking on how I could reduce the amount of code. So, I was thinking about using method injection, which should reduce the code to something like this:

[Route("api/v1/[controller]")]
public class ValuesController : Controller
{
    [HttpGet]
    public ValuesResponse Get(ValuesRequest request, IHandler<ValuesRequest, ValuesResponse> handler)
    {
        return handler.Handle(request);
    }

    [HttpGet("{id}")]
    public ValuesIdResponse Get(ValuesIdRequest request, IHandler<ValuesIdRequest, ValuesIdResponse> handler)
    {
        return handler.Handle(request);
    }
}

I was wondering if it is possible to do something like this in combination with controller params. I tried finding an answer on the web, however I could not find similar problem/solution.

Answer 1

Reference Action Injection with FromServices

Sometimes you don't need a service for more than one action within your controller. In this case, it may make sense to inject the service as a parameter to the action method. This is done by marking the parameter with the attribute [FromServices] as shown here:

public ValuesResponse Get(ValuesRequest request, [FromServices]IHandler<ValuesRequest, ValuesResponse> handler)
{
    return handler.Handle(request);
}

Answer 2

While the answer would work using [FromService] within your actions, I have another suggestion.

From what I understand by reading the code you have provided is, that you use some kind of CQRS. For that case I can suggest MediatR . You will then only need to inject one interface into your controller and send your request using the IMediator . This way you will keep your controller small and clean and you will not need to inject all the other handlers.

There is a nice and handy extension for Microsoft's IoC-Container to register all your handlers and all other necessary classes to use MediatR.

services.AddMediatR(typeof(Startup).Assembly);