static void Main(string[] args)
        {
            var Log = new LoggerConfiguration()
                        .WriteTo.ColoredConsole()
                        .WriteTo.RollingFile(@"Log-{Date}.txt")
                        .CreateLogger();

            string DataToPost = "{ \"payeePaymentReference\": \"0123456789\", " +
                                    "\"callbackUrl\": \"https://admin.dibspayment.com/\", " +
                                     "\"payerAlias\": \"46731596605\", " +
                                     "\"payeeAlias\": \"1231181189\", " +
                                     "\"amount\": \"100\", " +
                                     "\"currency\": \"SEK\", " +
                                     "\"message\": \"Order xx\" }";

            string URL = "https://mss.swicpc.bankgirot.se/swish-cpcapi/api/v1/paymentrequests/";

            //ServicePointManager.Expect100Continue = true;

            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls11;

            //Cert Challenge URL
            Uri requestURI = new Uri(URL);

            //Create the Request Object
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(requestURI);

            //Set the Request Object parameters
            req.ContentType = "application/json; charset=UTF-8";
            req.Method = "POST";
            req.ProtocolVersion = HttpVersion.Version10;

            X509Certificate cert = new X509Certificate2("Swish Merchant Test Certificate 1231181189.p12", "swish", X509KeyStorageFlags.Exportable | X509KeyStorageFlags.PersistKeySet);

            req.ClientCertificates.Add(cert);

            try
            {
                WebResponse response = req.GetResponse();

                String result = "";

                using (StreamReader rdr = new StreamReader(response.GetResponseStream()))
                {
                    result = rdr.ReadToEnd();
                }

                Log.Debug("Result: " + result);
            }
            catch (WebException e)
            {
                using (WebResponse response = e.Response)
                {
                    HttpWebResponse httpResponse = (HttpWebResponse)response;

                    Log.Information("Error code: {0}", httpResponse.StatusCode);

                    using (Stream data = response.GetResponseStream())
                    {
                        string text = new StreamReader(data).ReadToEnd();
                        Log.Information(text);
                    }
                }
            }
            Console.WriteLine(">>> Press enter to exit <<<");
            Console.ReadLine();
        }