protected Uri DiscoverPingbackLink(string page)
 {
   try
   {
     using (SgmlReader reader = new SgmlReader())
     {
       while (reader.ReadToFollowing("link"))
       {
         XElement link = XElement.Load(reader);
         if (link.Attribute("rel") != null && link.Attribute("rel").Value == "pingback")
           return new Uri(link.Attribute("href").Value); //TODO: deal with base Uri?
       }
     }
   }
   catch (Exception ex)
   {
     LogService.Error(ex);
   }
   return null;
 }