// POST api/GCM
        public HttpResponseMessage PostGCM(GCM gcm)
        {
            if (ModelState.IsValid)
            {
                gcm.Gcm_created_datetime = DateTime.Now;

                db.GCMs.Add(gcm);
                db.SaveChanges();

                HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, gcm.Gcm_id);
                response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = gcm.Gcm_id }));
                return response;
            }
            else
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }
        // PUT api/GCM/5
        public HttpResponseMessage PutGCM(int id, GCM gcm)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            if (id != gcm.Gcm_id)
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }

            db.Entry(gcm).State = EntityState.Modified;

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
            }

            return Request.CreateResponse(HttpStatusCode.OK);
        }