ASP MVC 5 Attribute routing not registering routes

Question

Overview

I'm currently trying to get attribute routing to work with my api controllers. It doesn't appear to be working, and I'm unsure why. I'm not sure if I'm missing a crucial step, or what the problem could be.

Problem

I'm trying to hit localhost/api/user/custom?test=1 but I get a 404 (I expect this to work)

If I hit localhost/api/customapi?test=1 I successfully get into my method

Why does the first url not work?

Setup

My setup is as follows:

CustomController.cs

[System.Web.Mvc.RoutePrefix("api")]
public class CustomApiController : ApiController
{
    [System.Web.Mvc.Route("user/custom")]
    [System.Web.Http.HttpGet]
    public async Task<CustomResponse> Get([FromUri] CustomRequest request)
    {
        //Work
    }
}

WebApiConfig.cs

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        ...(json serializer settings)...

        // Web API routes
        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
            );
    }
}

RouteConfig.cs

public static class RouteConfig
{
    public static void Register(RouteCollection routes, bool registerAreas = true)
    {
        if(registerAreas)
        {
            AreaRegistration.RegisterAllAreas();
        }

        //Ignore Routes
        ...

        //Register specific routes
        routes.MapRoute("HomeUrl", "home", new { controller = "Home", action = "Index" });
        .
        .

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

Global.asax.cs

public class Global : HttpApplication
{
    protected void Application_Start()
    {
        ....(app startup stuff)...

        GlobalConfiguration.Configure(WebApiConfig.Register);
        BundleConfig.Register(BundleTable.Bundles);

        ....(more app startup stuff)...

        RouteConfig.Register(RouteTable.Routes);
    }
}

Answer 1

I was using the wrong namespace in my routes.

[System.Web.Http.Route("")]   //Use this namespace for Web API 2
[System.Web.Mvc.Route("")]

[System.Web.Http.RoutePrefix("api")]  //Use this namespace Web API 2
[System.Web.Mvc.RoutePrefix("api")]