public void ProductEkle() { string productId = Guid.NewGuid().ToString(); string productName = tbxProductName.Text; string barkodNo = tbxBarkodNo.Text; decimal unitPrice = Convert.ToDecimal(tbxUnitPrice.Text); int quantity = Convert.ToInt32(tbxQuantity.Text); DateTime additionDate = DateTime.Now; CRUDHelper.AddProduct(new Product { ProductId = productId, ProductName = productName, BarkodNo = barkodNo, Quantity = quantity, UnitPrice = unitPrice, AdditionDate = additionDate }); foreach (var item in lbCategory.SelectedItems) { CRUDHelper.AddProductCategory(new ProductsCategories { ProductID = productId, CategoryID = (item as Categories).CategoryId, }); } MessageBox.Show("tamam"); }