Web API Cors problem

using this DLL:
  using System.Web.Http.Cors;



WebApiConfig:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Http;
using System.Web.Http.Cors;

namespace Angular2Web_API
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
 config.MapHttpAttributeRoutes();
  config.EnableCors(new EnableCorsAttribute(origins: "*", headers: "*", methods: "*"));
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }
}