获取远程XML文档

         private  XDocument GetXDocument( string  url)
        {
            Uri uri  =   new  Uri(url);
            System.Net.WebClient wb  =   new  System.Net.WebClient();
            wb.Proxy.Credentials  =  System.Net.CredentialCache.DefaultCredentials;
            MemoryStream ms  =   new  MemoryStream(wb.DownloadData(uri));
            System.Xml.XmlTextReader rdr  =   new  System.Xml.XmlTextReader(ms);
            XDocument doc  =  XDocument.Load(rdr);
             return  doc;
        }