c# xmlhttp POST提取遠程webservice數據

public?string?cancel(string?StudentID,string?Mobile)
????{
????string?data=null;
???data=?@"<?xml?version='1.0'?encoding='utf-8'?>
<soap:Envelope?xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'?xmlns:xsd='http://www.w3.org/2001/XMLSchema'?xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'>
??<soap:Header>
????<SPInfo?xmlns='https://211.138.113.176/xxtsync/Sync'>
??????<SPID>'01'</SPID>
??????<SPPassword>'B571B533872371AB85B1D0D02B22FEAA'</SPPassword>
????</SPInfo>
??</soap:Header>
??<soap:Body>
????<BusQX?xmlns='https://211.138.113.176/xxtsync/Sync'>
??????<StudentID>'11111111111'</StudentID>
??????<Mobile>'1111111111'</Mobile>
????</BusQX>
??</soap:Body>
</soap:Envelope>";
????????data?=?data.Replace("'",?"\"");
MSXML2.XMLHTTP?xmlhttp?=?new?MSXML2.XMLHTTP();???????
xmlhttp.open("POST",?"https://211.138.112.38/xxtsync/sync.asmx",?false,null,null);
xmlhttp.setRequestHeader("Content-Type",?"text/xml;?charset=utf-8");
xmlhttp.setRequestHeader("Content-Length",?data.Length.ToString());
xmlhttp.setRequestHeader("SOAPAction",?"https://211.138.113.176/xxtsync/Sync/BusQX");
int?n=xmlhttp.send(data);
Byte[]?b?=?(Byte[])xmlhttp.responseBody;//返回數據
string?s?=?System.Text.ASCIIEncoding.UTF8.GetString(b,?0,?b.Length);
return?n;
????}