C#模拟HTTP请求：GET与POST方法实现

static string HttpPost(string Url, string postDataStr)
        {
            try
            {
                CookieContainer cookie = new CookieContainer();

                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
                request.Method = "POST";
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = Encoding.UTF8.GetByteCount(postDataStr);
                request.CookieContainer = cookie;
                Stream myRequestStream = request.GetRequestStream();
                StreamWriter myStreamWriter = new StreamWriter(myRequestStream, Encoding.GetEncoding("gb2312"));
                myStreamWriter.Write(postDataStr);
                myStreamWriter.Close();

                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                response.Cookies = cookie.GetCookies(response.ResponseUri);
                Stream myResponseStream = response.GetResponseStream();
                StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));
                string retString = myStreamReader.ReadToEnd();
                myStreamReader.Close();
                myResponseStream.Close();

                return retString;
            }
            catch (Exception ex)
            {
                return null;
            }