CallService

 private string CallService(string url, string postData, string contentType)
        {
            try
            {
                HttpWebRequest httpWReq = (HttpWebRequest)WebRequest.Create(url);

                byte[] data = System.Text.Encoding.UTF8.GetBytes(postData);

                //string contentType = radioBtnJson.Checked ? "text/json" : "text/xml";
                //contentType = "application/x-www-form-urlencoded";

                httpWReq.Method = "POST";
                httpWReq.ContentType = contentType + "; charset=utf-8";
                httpWReq.ContentLength = data.Length;

                using (Stream stream = httpWReq.GetRequestStream())
                {
                    stream.Write(data, 0, data.Length);
                }

                HttpWebResponse response = (HttpWebResponse)httpWReq.GetResponse();

                string responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

                return responseString;
            }
            catch (Exception ex)
            {
                txtResult.Text += ex.ToString();
            }
            return null;
        }