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;
        }