c#模拟post发送

public string HttpPost(string url, string Data)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "POST"; //请求类型
request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8"; //提交数据类型

byte[] reqdata = Encoding.UTF8.GetBytes(Data); //将数据转化为字节
using (Stream req = request.GetRequestStream())
{
req.Write(reqdata, 0, reqdata.Length);//将数据写入流
req.Close();
}


// StreamWriter myreq = new StreamWriter(req, Encoding.GetEncoding("utf-8"));
// myreq.Write(Data);
//myreq.Close();
try
{
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream res = response.GetResponseStream();
StreamReader myres = new StreamReader(res, Encoding.GetEncoding("utf-8"));
string retData = myres.ReadToEnd();
res.Close();
myres.Close();
return retData;
}
catch (WebException e)
{
MessageBox.Show(e.ToString());
}
return "失败";