public ApiResponse <IEnumerable <InventoryItem> > AddUpdate([FromBody] InventoryItem item) { item.LastUpdated = DateTime.Now; var existing = _context.Find <InventoryItem>(new object[] { item.ProductId }); if (existing == null) { _context.Add(item); } else { existing.Quantity = item.Quantity; } _context.SaveChanges(); return(GetAll()); }