HttpWebRequest.GetResponse()是自动在响应完成后调用吗?该怎么处理

string PostData = Session["QQ"] + ";00;" + num + ";" + Session["LoginKey"] + ";";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(reqUrl);
request.Method = "POST";
byte[] bytes = Encoding.GetEncoding("GB2312").GetBytes(PostData);
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = bytes.Length;     
Stream sr = request.GetRequestStream();
sr.Write(bytes, 0, bytes.Length);
sr.Dispose();
WebResponse response = request.GetResponse();