// POST api/Orders
        public HttpResponseMessage PostOrder(Order order)
        {
            if (!ModelState.IsValid)
            {
                return(Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState));
            }

            order.TrackingState = TrackingState.Added;
            _dbContext.ApplyChanges(order);

            try
            {
                _dbContext.SaveChanges();
            }
            catch (DbUpdateException ex)
            {
                if (_dbContext.Orders.Any(o => o.OrderId == order.OrderId))
                {
                    return(Request.CreateErrorResponse(HttpStatusCode.Conflict, ex));
                }
                throw;
            }

            _dbContext.LoadRelatedEntities(order);
            order.AcceptChanges();

            HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, order);

            response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = order.OrderId }));
            return(response);
        }