private void BtnModifyProduct_Click(object sender, RoutedEventArgs e)
        {
            selectedIndex = DataGridProducts.SelectedIndex;

            if (selectedIndex != -1)
            {
                selectedProduct = productList[selectedIndex];

                //message to verify edit
                string           msg       = "Are you sure you want to edit: " + selectedProduct.ProductName + "?";
                MessageBoxResult boxResult = MessageBox.Show(msg, "Accept Modify", MessageBoxButton.YesNo,
                                                             MessageBoxImage.Question);
                if (boxResult == MessageBoxResult.Yes)
                {
                    Window WindowProdAdd = new ProductAdd(selectedProduct);
                    WindowProdAdd.Show();
                    Close();
                }
            }
        }