Hàm Get sudomain in trong URL - the URL to get the sub domain from

Hàm Get sudomain in trong URL - The URL to get the sub domain from

public static string GetSubDomain(Uri url)
{      
   if (url.HostNameType == UriHostNameType.Dns)
   {
         var host = url.Host;
         if (host.Split('.').Length > 2)
         {
               var lastIndex = host.LastIndexOf(".");
               var index = host.LastIndexOf(".", lastIndex - 1);
               return host.Substring(0, index);
          }
    }

    return null;
}

Hàm Get sudomain in trong URL - The URL to get the sub domain from