C# ile xml request ve response(Soap)

string WSUrl = "http://sdp.test.com.tr/proxy/external"; //Servis Adresiminiz
string soap = "<s:Envelope xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\"><s:Header><h:token xmlns:h=\"http://sdp.test.com.tr/mapping/generated\" xmlns=\"http://sdp.test.com.tr/mapping/generated\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">" +
"<sessionId>" + sessionId + "</sessionId></h:token>" +
"</s:Header><s:Body xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"><TestInput xmlns=\"http://sdp.test.com.tr/mapping/generated\">" +
"<REFERANS_ID>referansID</REFERANS_ID>" +
"<REQUEST_TIME>2014-12-18 09:11:59.931</REQUEST_TIME>" +
"<DELIVERY_CHANNEL>ECDS</DELIVERY_CHANNEL>" +
"</TestInput></s:Body></s:Envelope>";

WebRequest req = WebRequest.Create(WSUrl);
req.Credentials = System.Net.CredentialCache.DefaultCredentials;
req.Headers.Add(String.Format("SOAPAction:{0}", "http://sdp.test.com.tr/services/action/test")); //Action adresiminz
req.ContentType = "text/xml;charset=\"utf-8\"";
req.Method = "POST";
Stream stm = req.GetRequestStream();
using (StreamWriter stmw = new StreamWriter(stm))
{
    stmw.Write(soap);
}

string responseString = "";
using (WebResponse response = req.GetResponse())
{
Stream responseStream = response.GetResponseStream();
using (StreamReader reader = new StreamReader(responseStream))
{
    responseString = reader.ReadToEnd();
}
}

#region Debit - Response işlemi

if (!String.IsNullOrEmpty(responseString))
{
    XmlDocument document = new XmlDocument();
    document.LoadXml(responseString);
    XmlNamespaceManager manager = new XmlNamespaceManager(document.NameTable);
    manager.AddNamespace("sdp", "http://sdp.test.com.tr/mapping/generated");
    manager.AddNamespace("so", "so:http://sdp.test.com/mapping/TSO");
    XmlNodeList xnList = document.SelectNodes("//sdp:RefId_DirectDebitOutput", manager);

   foreach (XmlNode xn in xnList)
   {
       var getTSOresult = xn["so:TSOresult"]; //Dönen değerleri alabiliriz.
   }
}

#endregion