Asp.net 子域不使用默认路由

我在

RouteConfig.cs

中创建了一个子域路由类，如下所示：

public class SubdomainRoute : RouteBase
    {
        public override RouteData GetRouteData(HttpContextBase httpContext)
        {
            if (httpContext.Request == null || httpContext.Request.Url == null)
            {
                return null;
            }
            var host = httpContext.Request.Url.Host;
            var index = host.IndexOf(".");
            string[] segments = httpContext.Request.Url.PathAndQuery.TrimStart('/').Split('/');
            if (index < 0)
            {
                return null;
            }
            var subdomain = host.Substring(0, index);
            string[] blacklist = { "www", "yourdomain", "mail","localhost" };
            if (blacklist.Contains(subdomain))
            {
                return null;
            }
            string controller = (segments.Length > 0) ? segments[0] : "Home";
            if (controller == "")
                controller = "Home";
            string action = (segments.Length > 1) ? segments[1] : "Index";
            var routeData = new RouteData(this, new MvcRouteHandler());
            routeData.Values.Add("controller", controller);
            routeData.Values.Add("action", action);
            routeData.Values.Add("subdomain", subdomain);
            return routeData;
        }
        public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
        {
            return null;
        }
    }

我的索引函数是：

public string Index(string category, string subcategory, string lowcategory,int? id)

---

现在链接

http://localhost:29808/Home/Index/mobiles/Htc/M8/3

工作正常，但与子域一起，其不工作

电子设备。本地主机：29808/Home/Index/mobiles/HTC/M8/3

。（类别和子类别中显示空值）。如果必须包含哪些内容才能使其正常工作？

您是否收到空引用异常？不，我没有收到任何异常

public string Index(string category, string subcategory, string lowcategory,int? id)