Abstract common code between MVC 5 Controllers and Web Api Controllers

Question

I have an application with an ASP .Net MVC 5 front end and a Web Api 2 service layer and I would like to use dependency injection so the MVC 5 controllers only rely on abstractions for the Web Api 2 ones.

Since the Web Api controllers mostly use this kind of signature:

public IHttpActionResult SomeMethod(){ return Ok(); }

my first thought was that the interface should be:

IHttpActionResult SomeMethod();

Now I have a class library with the interfaces for the services but that means that this class library would need a reference to System.Web.Http in order to use the IHttpActionResult interface in the signatures.

I have two questions:

Fist this feels out right wrong that this library has a reference to System.Web.Http, is there an alternative to this?
If there isn't an alternative, when I try to add the reference I only get an older version of the library which does not have a definition for that interface, where can I get the correct version from?

Thank you.

pm100 · Accepted Answer · 2015-03-05 22:08:27Z

1

I would shove the common logic into a common library with 'normal' inputs and outputs. The two transports (MVC and web api) can then call this library

answered Mar 5, 2015 at 22:08

pm100

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Comments

shenku · Accepted Answer · 2015-03-05 22:25:46Z

It really depends on what you are trying to achieve - aka how much abstraction you want to introduce.

If you wan't to move all the common business logic into a service for re-use from here, and potentially anywhere then yes you want to get rid of the System.Web.Http references.

Do this by having a clean interface/implimentation that simply return the result of the actions something like this:

public interface ICustomerService 
{
    BaseResponse DoSomething(BaseRequest request);
}

public abstract class BaseResponse 
{
    public bool IsSuccess { get; set; }
    public IList<string> Errors { get; set; }
}

/*
Note: BaseResponse & BaseRequest, follow the command pattern for passing information you would impliment concrete versions of these.
*/

I then allow the controllers for both Web & Api control how to use this BaseResponse to er...respond.

So maybe create a BaseController, and BaseApiController:

For example:

public abstract class BaseApiController : ApiController 
{
        protected HttpResponseMessage HandleResponse(BaseResponse response)
        {
            return
                !response.IsSuccess
                    ? Request.CreateErrorResponse(HttpStatusCode.BadRequest, response.Errors )
                    : Request.CreateResponse(HttpStatusCode.OK, response);
        }
}

And:

public abstract class BaseController : Controller
{
    protected ActionResult HandleResponse(BaseResponse response, string redirectToAction)
    {
        if (response.IsSuccess) 
            return RedirectToAction(redirectToAction);

        foreach (var error in response.Errors)
        {
            ModelState.AddModelError(string.Empty, error);
        }

        return View();
    }
}

Then in WebApi Controller:

public HttpResponseMessage DoAction(string param1)
    {
        return HandleResponse(_customerService.DoSomething(new DoActionRequest { Param1 = param1 }));
    }

And in the Web Controller

public ActionResult DoAction(ViewModel viewModel)
    {
        var response = _customerService.DoSomething(new DoActionRequest { Param1 = param1 });

        return HandleResponse(response, "Success");
    }

In this way all busienss logic is tucked away and resusable, and the ApiController and Controllers can respond in their own unique ways.

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