Elimde sms firmasından aldığım api var programa ekliyorum sms atıyor. ama benim istediğim mesaj metni ve cep telefon numarasını textboxdan çekmek bir türlü yapamadım yardımcı olabilirmisiniz

<MessageText>Mesaj metni</MessageText>

                            <IsCheckBlackList>0</IsCheckBlackList> 

                             <ReceiverList>

                             <Receiver>905303626490</Receiver>

                             <Receiver>905051234567</Receiver>

                            </ReceiverList>

public static void CallWebService()

    {

            var _url = "https://webservice.asistiletisim.com.tr/SmsProxy.asmx";

            var _action = "https://webservice.asistiletisim.com.tr/SmsProxy/sendSms";

      XmlDocument soapEnvelopeXml = new XmlDocument();

            soapEnvelopeXml.LoadXml(@"<soapenv:Envelope xmlns:soapenv=""http://schemas.xmlsoap.org/soap/envelope/"" xmlns=""https://webservice.asistiletisim.com.tr/SmsProxy"">

                      <soapenv:Header/>

                      <soapenv:Body>

                       <sendSms>

                         <requestXml><![CDATA[<SendSms>

                            <Username>xxxx</Username>

                            <Password>xxxxx</Password>

                            <UserCode>xxxxx</UserCode>

                            <AccountId>xxxxxx</AccountId>

                            <Originator>xxxxxx</Originator>

                            <ValidityPeriod>60</ValidityPeriod>

                            <SendDate/>

                            <MessageText>This is one to many sending example..</MessageText>

                            <IsCheckBlackList>0</IsCheckBlackList> 

                             <ReceiverList>

                             <Receiver>905303626490</Receiver>

                             <Receiver>905051234567</Receiver>

                            </ReceiverList>

                          </SendSms>]]></requestXml>

                       </sendSms>

                      </soapenv:Body>

                    </soapenv:Envelope>");

      HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(_url);

      webRequest.Headers.Add("SOAPAction", _action);

      webRequest.ContentType = "text/xml;charset=\"utf-8\"";

      webRequest.Accept = "text/xml";

      webRequest.Method = "POST";

      using (Stream stream = webRequest.GetRequestStream())

      {

        soapEnvelopeXml.Save(stream);

      }

      IAsyncResult asyncResult = webRequest.BeginGetResponse(null, null);

      asyncResult.AsyncWaitHandle.WaitOne();

      string soapResult;

      using (WebResponse webResponse = webRequest.EndGetResponse(asyncResult))

      {

        using (StreamReader rd = new StreamReader(webResponse.GetResponseStream()))

        {

          soapResult = rd.ReadToEnd();

        }

        Console.Write(soapResult);

      }

    }