FCM Notification based on API

FCMAPINotification.cs

public class Notifications
    {

        public string SendNotification(GcmNotiInputModel model)
        {
            try
            {
                string GoogleAppID = Config.BrowserKey;
                var SENDER_ID = Config.SenderId;

                WebRequest tRequest;
                tRequest = WebRequest.Create("https://fcm.googleapis.com/fcm/send");
                tRequest.Method = "post";
                tRequest.ContentType = " application/x-www-form-urlencoded;charset=UTF-8";
                tRequest.Headers.Add(string.Format("Authorization: key={0}", GoogleAppID));

                tRequest.Headers.Add(string.Format("Sender: id={0}", SENDER_ID));

                // string postData = "{ 'registration_id': [ '" + regId + "' ], 'data': {'message': '" + txtMsg.Text + "'}}";

                // title=Title Text
                // message=This is a test message
                // type=1
                // sound=0
                // vibrate=1

                string postData = "collapse_key=score_update&time_to_live=108&delay_while_idle=1&data.message=" + model.Message
                    + "&data.title=" + model.Title
                    + "&data.type=" + model.Type
                    + "&data.sound=" + model.Sound
                    + "&data.vibrate=" + model.Vibrate
                    + "&data.time=" + System.DateTime.Now.ToString()+model.extra
                    + "&registration_id=" + model.DeviceID + "";
                Byte[] byteArray = Encoding.UTF8.GetBytes(postData);
                tRequest.ContentLength = byteArray.Length;

                Stream dataStream = tRequest.GetRequestStream();
                dataStream.Write(byteArray, 0, byteArray.Length);
                dataStream.Close();

                WebResponse tResponse = tRequest.GetResponse();

                dataStream = tResponse.GetResponseStream();

                StreamReader tReader = new StreamReader(dataStream);

                String sResponseFromServer = tReader.ReadToEnd();

                tReader.Close();
                dataStream.Close();
                tResponse.Close();
                return sResponseFromServer;
            }
            catch (Exception ex)
            {
                return ex.Message;
            }
        }

    }