Line needed to enable CORS in Web API 5.0

WebAPIConfig.cs

public static class WebApiConfig {
    public static void Register(HttpConfiguration config) {
            // Web API configuration and services
            // Configure Web API to use only bearer token authentication.

            config.Formatters.XmlFormatter.SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("multipart/form-data"); config.SuppressDefaultHostAuthentication(); config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));

                    // Web API routes
                    config.MapHttpAttributeRoutes();

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

                        //Needed for CORS
                        EnableCorsAttribute cors = new EnableCorsAttribute("*", "*", "*"; config.EnableCors(cors);

                        }
                    }