asp.net – 如何在MVC4中扩展内容协商行为？

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

        routes.MapHttpRoute(
            name: "Api with extension",routeTemplate: "api/{controller}.{ext}/{id}",defaults: new { id = RouteParameter.Optional,ext = RouteParameter.Optional }
        );

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

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

    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);

        GlobalConfiguration.Configuration.Formatters.XmlFormatter.AddUriPathExtensionMapping("xml","text/xml");
        GlobalConfiguration.Configuration.Formatters.JsonFormatter.AddUriPathExtensionMapping("json","application/json");
        BundleTable.Bundles.RegisterTemplateBundles();
    }