// POST api/Categories
        public HttpResponseMessage PostCategory(Category category)
        {
            if (ModelState.IsValid)
            {
                db.Categories.Add(category);
                db.SaveChanges();

                HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, category);
                response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = category.Id }));
                return response;
            }
            else
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }
        }
        // PUT api/Categories/5
        public HttpResponseMessage PutCategory(int id, Category category)
        {
            if (ModelState.IsValid && id == category.Id)
            {
                db.Entry(category).State = EntityState.Modified;

                try
                {
                    db.SaveChanges();
                }
                catch (DbUpdateConcurrencyException)
                {
                    return Request.CreateResponse(HttpStatusCode.NotFound);
                }

                return Request.CreateResponse(HttpStatusCode.OK);
            }
            else
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }
        }