C#方式Post方式发送xml及接收

RT，我需要做个demo aa.aspx.cs里面post一个xml格式数据到bb.aspx页面该如何做？
我试了以下代码

[align=left] string postXml = "<?xml version=\"1.0\" encoding=\"GBK\"?><sync_req><head><id>WXCS</id><pwd>zs@0822*hxyd</pwd></head>" +
               "<body><area>0760</area><serviceid>ZSWX</serviceid><appName>SZtest</appName><phoneList><phone><phoneNum></phoneNum>" +
               "<action>A</action> <position_type>A</position_type><ue_type>1</ue_type><servicetype>AL</servicetype><status>S</status> <locationTime>1</locationTime>" +
               "</phone> </phoneList></body></sync_req>";
            string url = "http://localhost:3496/BusRoute.aspx";
            HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(url);
            myRequest.Method = "POST";
            myRequest.ContentType = "application/x-www-form-urlencoded";
            myRequest.ContentLength = postXml.Length;
            Stream newStream = myRequest.GetRequestStream();
            byte[] data = Encoding.GetEncoding("GB2312").GetBytes(postXml);
            // 发送数据
            newStream.Write(data, 0, data.Length);
            HttpWebResponse res = myRequest.GetResponse() as HttpWebResponse;
            StreamReader sr = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
            String ret = sr.ReadToEnd();
            XmlDocument doc = new XmlDocument();
            doc.LoadXml(ret);
            string mes = doc.GetElementsByTagName("resultInfo")[0].InnerText;[/align]

结果在HttpWebResponse res = myRequest.GetResponse() as HttpWebResponse;执行到这句是报
远程服务器返回错误: (500) 内部服务器错误。

代码没有问题，可是url改成“http://120.197.89.32/ELIS/lbsServle”就可以正确返回结果，现在我想在本地程序http://localhost:3496/BusRoute.aspx测试改怎么做？

求高手解决！！！！！ --------------------编程问答-------------------- XmlDocument   XmlD=new   XmlDocument();
Xml.LoadXml(Path);
RequestXml.OuterXml
Stream   oWriter=null;
bool   bResult=true;
byte[]   data   =   System.Text.Encoding.UTF8.GetBytes(Xml.OuterXml);       //转换xml内的数据为byte的数组
HttpWebRequest   myRequest   =   (HttpWebRequest)WebRequest.Create(url);   //url，函数接口地址

myRequest.Method   =   "POST ";
myRequest.Headers.Add( "SOAPAction ",   SoapAction);   //指定访问Web   Service的命名空间及使用方法
myRequest.Headers.Add( "ContentType ", "text/xml;   charset=utf-8 ");   //指定字符集
myRequest.Headers.Add( "ContentLength ",data.Length.ToString());

try
{
oWriter=myRequest.GetRequestStream();//获取与远程Web   Service的联络
oWriter.Write(data,0,data.Length);//发送数据
oWriter.Close();   //关闭连接
}
catch(Exception)
{
//oWriter.Close();
bResult=false;

}

Stream   oReader=null;

if   (bResult)   //只有发送数据正常时，才读取响应
{

try
{
HttpWebResponse   oResponse=(HttpWebResponse)myRequest.GetResponse();

oReader   =oResponse.GetResponseStream()   ;
outxml.Load(oReader);

oReader.Close();

}
catch(Exception   )
{
}
}

补充：.NET技术 ,  ASP.NET