WebAPI and ODataController return 406 Not Acceptable

The order in which the routes are configured has an impact. In my case, I also have some standard MVC controllers and help pages. So in Global.asax:

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    GlobalConfiguration.Configure(config =>
    {
        ODataConfig.Register(config); //this has to be before WebApi
        WebApiConfig.Register(config); 

    });
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
}

The filter and routeTable parts weren't there when I started my project and are needed.

ODataConfig.cs:

public static void Register(HttpConfiguration config)
{
    config.MapHttpAttributeRoutes(); //This has to be called before the following OData mapping, so also before WebApi mapping

    ODataConventionModelBuilder builder = new ODataConventionModelBuilder();

    builder.EntitySet<Site>("Sites");
    //Moar!

    config.MapODataServiceRoute("ODataRoute", "api", builder.GetEdmModel());
}

WebApiConfig.cs:

public static void Register(HttpConfiguration config)
{
    config.Routes.MapHttpRoute( //MapHTTPRoute for controllers inheriting ApiController
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
    );
}

And as a bonus, here's my RouteConfig.cs:

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

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

This has to be in that EXACT ORDER. I tried moving the calls around and ended up with either MVC, Api or Odata broken with 404 or 406 errors.

So I can call:

localhost:xxx/ -> leads to help pages (home controller, index page)

localhost:xxx/api/ -> leads to the OData $metadata

localhost:xxx/api/Sites -> leads to the Get method of my SitesController inheriting from ODataController

localhost:xxx/api/Test -> leads to the Get method of my TestController inheriting from ApiController.

Set routePrefix to "api".

ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
builder.EntitySet<CustomerType>("CustomerType");

config.MapODataServiceRoute(routeName: "ODataRoute", routePrefix: "api", model: builder.GetEdmModel());

Which OData version are you using? Check for correct namespaces, for OData V4 use System.Web.OData, for V3 System.Web.Http.OData. Namespaces used in controllers have to be consistent with the ones used in WebApiConfig.

If you are using OData V4, replace using System.Web.Http.OData;

With using Microsoft.AspNet.OData; (Please check the comments for the latest library)

in the ODataController works for me.