Have Microsoft changed how ASP.NET MVC deals with duplicate action method names?

Question

I might be missing something here, but in ASP.NET MVC 4, I can't get the following to work.

Given the following controller:

public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }

    [HttpPost]
    public ActionResult Index(string order1, string order2)
    {
        return null;
    }
}

and it's view:

@{
    ViewBag.Title = "Home";
}

@using (Html.BeginForm())
{
    @Html.TextBox("order1")<br />
    @Html.TextBox("order2")
    <input type="submit" value="Save"/>
}

When start the app, all I get is this:

The current request for action 'Index' on controller type 'HomeController' is ambiguous between the following action methods: System.Web.Mvc.ActionResult Index() on type ViewData.Controllers.HomeController System.Web.Mvc.ActionResult Index(System.String, System.String) on type ViewData.Controllers.HomeController

Now, in ASP.NET MVC 3 the above works fine, I just tried it, so what's changed in ASP.NET MVC 4 to break this?

OK there could be a chance that I'm doing something silly here, and not noticing it.

EDIT:

I notice that in the MVC 4 app, the Global.asax.cs file did not contain this:

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

    routes.MapRoute(
        "Default", // Route name
        "{controller}/{action}/{id}", // URL with parameters
        new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
    );
}

which the MVC 3 app does, by default. So I added the above to the MVC 4 app but it fails with the same error. Note that the MVC 3 app does work fine with the above route. I'm passing the "order" data via the Request.Form.

EDIT: In the file RouteConfig.cs I can see RegisterRoutes is executed, with the following default route:

routes.MapRoute(
    name: "Default",
    url: "{controller}/{action}/{id}",
    defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional });

I still get the original error, regards ambiguity between which Index() method to call.

Did you change the default routing? If your default routing has two optional parameters then it won't be able to tell the difference between the two. — Erik Funkenbusch, Dec 14 '12 at 18:11
If you want to overload the action name, you need to use `ActionName` attribute. Answered here: http://stackoverflow.com/questions/436866/can-you-overload-controller-methods-in-asp-net-mvc — Ray Cheng, Dec 14 '12 at 18:19
@RayCheng - he's not overloading the action name in that way, he's using normal HttpPost method. — Erik Funkenbusch, Dec 14 '12 at 18:24
Jason, You don't add that method to Global.asax, there is now a file in App_Start called RouteConfig.cs, and that method is called from global.asax — Erik Funkenbusch, Dec 14 '12 at 18:26

score 10 · Accepted Answer · answered Dec 15 '12 at 17:02

Because MVC4 ships with ASP.Net Web.API you can potentially reference two HttpPostAttribute (the same applies to the other attributes like HttpGet, etc.):

System.Web.Mvc.HttpPostAttribute is used by ASP.Net MVC so you need to use it on actions inside Controller derived controllers
System.Web.Http.HttpPostAttribute is used by ASP.Net Web.API so you need to use it on actions inside ApiController derived controllers

You have acidentally referenced System.Web.Http.HttpPostAttribute in your code. Change it to use the right attribute and it should work correctly:

public class HomeController : Controller
{
    public ActionResult Index()
    {
        return View();
    }

    [System.Web.Mvc.HttpPost]
    public ActionResult Index(string order1, string order2)
    {
        return null;
    }
}

Have Microsoft changed how ASP.NET MVC deals with duplicate action method names?

1 Answers1