int g = 0;
                    for (int i = 0; i < 40; i++)
                    {
                    g++;
                        SendRequest("POST data", "http://www.site.com/page.php");
                        label_num.Text = g.ToString();
                        tb_gameslot.Text = ((int)Convert.ToInt32(tb_gameslot.Text) + 1).ToString();
                    }

private void SendRequest(string postData, string url)
        {

            HttpWebRequest wr = WebRequest.Create(url) as HttpWebRequest;
            wr.Method = "POST";
            wr.ContentType = "application/x-www-form-urlencoded";
            wr.UserAgent = "agent/10.0.2 CFNetwork/672.1.14 Darwin/14.0.0";
            wr.Accept = "*/*";
            
            wr.Proxy.Credentials = CredentialCache.DefaultCredentials;
wr.BeginGetRequestStream(new AsyncCallback(RequestCorrelationStart), wr);
        }

        private static void RequestCorrelationStart(IAsyncResult start_result)
        {
            HttpWebRequest start_request = start_result.AsyncState as HttpWebRequest;
            StreamWriter post_data_writer = new StreamWriter(start_request.EndGetRequestStream(start_result));
            post_data_writer.Write(_parameters);

            post_data_writer.Close();
            start_request.BeginGetResponse(new AsyncCallback(RequestCorrelationResponse), start_request);
        }

        private static void RequestCorrelationResponse(IAsyncResult response_result)
        {
            HttpWebRequest response_request = response_result.AsyncState as HttpWebRequest;
            HttpWebResponse response = response_request.EndGetResponse(response_result) as HttpWebResponse;
            // answer from getPostRequest.php
            StreamReader response_reader = new StreamReader(response.GetResponseStream());
            string response_string = response_reader.ReadToEnd();
        }