Working sample for FirstData e4 web api

JSON format, search for c# sample code to get sample with XML request

        string json_string = "{\"gateway_id\":\"AD8549-05\",\"password\":\"ts8by19q\",\"transaction_type\":\"00\",\"amount\":101,\"cardholder_name\":\"Allen Abc\",\"cc_number\":\"5454545454545454\",\"cc_expiry\":\"0315\",\"cc_verification_str2\":\"123\"}";

        //SHA1 hash on XML string
        ASCIIEncoding encoder = new ASCIIEncoding();
        byte[] json_byte = encoder.GetBytes(json_string);


        SHA1CryptoServiceProvider sha1_crypto = new SHA1CryptoServiceProvider();
        string hash = BitConverter.ToString(sha1_crypto.ComputeHash(json_byte)).Replace("-", "");
        //string hash = Convert.ToBase64String(sha1_crypto.ComputeHash(json_byte));
        string hashed_content = hash.ToLower();

        //assign values to hashing and header variables
        string method = "POST\n";
        //string type = "application/xml\n";//REST XML
        string type = "application/json; charset=UTF-8\n";//REST XML
        string time = DateTime.UtcNow.ToString("yyyy-MM-ddTHH:mm:ssZ");
        string url = "/transaction/v12";
        string keyID = "43490";//key ID
        string key = "zq2cDOLvYjyVy1liiJL_dolb31Atey7E";//Hmac key
        string hash_data = method + type + hashed_content + "\n" + time + "\n" + url;
        //hmac sha1 hash with key + hash_data
        HMAC hmac_sha1 = new HMACSHA1(Encoding.UTF8.GetBytes(key)); //key
        byte[] hmac_data = hmac_sha1.ComputeHash(Encoding.UTF8.GetBytes(hash_data)); //data
        //base64 encode on hmac_data
        string base64_hash = Convert.ToBase64String(hmac_data);

        //begin HttpWebRequest // use https://api.globalgatewaye4.firstdata.com/transaction/v12 for production
        HttpWebRequest web_request = (HttpWebRequest)WebRequest.Create("https://api.demo.globalgatewaye4.firstdata.com/transaction/v12");
        web_request.Method = "POST";
        //web_request.Accept = "application/xml";
        web_request.Accept = "application/json";
        web_request.Headers.Add("x-gge4-date", time);
        web_request.Headers.Add("x-gge4-content-sha1", hashed_content);
        //web_request.ContentLength = json_string.Length;
        //web_request.ContentLength = Encoding.UTF8.GetByteCount(json_string);
        //web_request.ContentType = "application/xml";
        web_request.ContentType = "application/json; charset=UTF-8";
        web_request.Headers["Authorization"] = "GGE4_API " + keyID + ":" + base64_hash;


        // send request as stream
        StreamWriter xml = null;
        //Encoding enc = new UTF8Encoding(false);
        //xml = new StreamWriter(web_request.GetRequestStream(), Encoding.UTF8);
        //xml.Write("{\"gateway_id\":\"AD8549-05\",\"password\":\"ts8by19q\",\"transaction_type\":\"00\",\"amount\":101,\"cardholder_name\":\"Allen Abc\",\"cc_number\":\"5454545454545454\",\"cc_expiry\":\"0315\",\"cc_verification_str2\":\"123\"}");

        xml = new StreamWriter(web_request.GetRequestStream());
        xml.Write(json_string);
        xml.Close();


        //get response and read into string
        string response_string;
        try
        {
            HttpWebResponse web_response = (HttpWebResponse)web_request.GetResponse();
            using (StreamReader response_stream = new StreamReader(web_response.GetResponseStream()))
            {
                response_string = response_stream.ReadToEnd();
                response_stream.Close();
            }

            Console.Write(System.Web.HttpUtility.HtmlEncode(json_string));
            Console.Write(System.Web.HttpUtility.HtmlEncode(response_string));
        }
        catch (WebException ew)
        {
            using (WebResponse response = ew.Response)
            {
                HttpWebResponse httpResponse = (HttpWebResponse)response;
                Console.WriteLine("Error code: {0}", httpResponse.StatusCode);
                using (Stream data = response.GetResponseStream())
                using (var reader = new StreamReader(data))
                {
                    string text = reader.ReadToEnd();
                    Console.WriteLine(text);
                }
            }
        }
        catch (System.Exception ex)
        {
            //error.Text = ex.ToString();
            Console.Write(ex);
        }