public async Task <ActionResult> Post([FromBody] PurchaseInformations purchaseInformations)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest(ModelState));
            }
            else if (purchaseInformations == null)
            {
                return(NotFound());
            }
            db.PurchaseInformations.Add(purchaseInformations);
            await db.SaveChangesAsync();

            return(NoContent());
        }
        public async Task <ActionResult> Post([FromBody] Supplier supplier)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest(ModelState));
            }
            else if (supplier == null)
            {
                return(NotFound());
            }
            this.db.Suppliers.Add(supplier);
            await db.SaveChangesAsync();

            return(NoContent());
        }
        public async Task <ActionResult> Post([FromBody] Product product)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest(ModelState));
            }
            else if (product == null)
            {
                return(NotFound());
            }
            db.Products.Add(product);
            await db.SaveChangesAsync();

            return(NoContent());
        }