ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);                X509Certificate cer = new X509Certificate(cert, password,X509KeyStorageFlags.PersistKeySet|X509KeyStorageFlags.Exportable|X509KeyStorageFlags.MachineKeySet);                HttpWebRequest webrequest = (HttpWebRequest)HttpWebRequest.Create(url);                webrequest.ClientCertificates.Add(cer);                webrequest.Method = "post";                webrequest.Proxy = null;                Encoding encoding = Encoding.UTF8;                    byte[] databyte = encoding.GetBytes(xml);                    webrequest.ContentLength = databyte.Length;                    Stream stream = webrequest.GetRequestStream();                    stream.Write(databyte, 0, databyte.Length);                    stream.Close();                    string result = string.Empty;                   webrequest.KeepAlive = false;                   HttpWebResponse webreponse = (HttpWebResponse)webrequest.GetResponse();                   Stream responsestream = webreponse.GetResponseStream();                   using (StreamReader reader = new StreamReader(responsestream))               {                   result = reader.ReadToEnd();                   writeLogs.writelog("退款接口返回结果:" + result);               }