subdomain does not work with default route - asp.net

Question

I have created a sub-domain route class in RouteConfig.cs as:
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;
}
}
I updated RegisterRoutes function to :
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.Add(new SubdomainRoute());
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{category}/{subcategory}/{lowcategory}/{id}",
defaults: new { controller = "Home", action = "Index",category=UrlParameter.Optional,subcategory=UrlParameter.Optional,lowcategory=UrlParameter.Optional, id = UrlParameter.Optional }
);
}
My Index function is :
public string Index(string category, string subcategory, string lowcategory,int? id)
Now the link http://localhost:29808/Home/Index/mobiles/Htc/M8/3 is working fine but with subdomain its not working electronics.localhost:29808/Home/Index/mobiles/HTC/M8/3. (It shows null in category and subcategory). What else if have to include to make it work?