// POST api/Producers
        public HttpResponseMessage PostProducer(Producer producer)
        {
            if (ModelState.IsValid)
            {
                db.Producers.Add(producer);
                db.SaveChanges();

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

            if (id != producer.ProducerId)
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }

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

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

            return Request.CreateResponse(HttpStatusCode.OK);
        }