UC_Sales

private void button_IncreaseAmount_Click(object sender, EventArgs e)
        {
            if (listViewCart.SelectedItems.Count == 0)
            {
                MessageBox.Show("Select row...");
                return;
            }

            int quantity = bs.GetBookByBarcode(int.Parse(textBox_Barcode.Text)).Number;
            if (quantity <= 0)
            {
                MessageBox.Show("There are no books left...");
                return;
            }
            else if (listViewCart.FindItemWithText(textBox_BookTitle.Text) != null)
            {
                if (int.Parse(listViewCart.FindItemWithText(textBox_BookTitle.Text).SubItems[1].Text) == quantity)
                {
                    MessageBox.Show("Can't add more than available!");
                    return;
                }
            }

            if (listViewCart.SelectedItems.Count > 0)
            {
                ListViewItem item = listViewCart.SelectedItems[0];
                amount = 0;
                item.SubItems[1].Text = int.Parse(item.SubItems[1].Text) + 1 + "";
                CalculateAmount();
            }
            else
            {
                MessageBox.Show("Select row...");
                return;
            }
        }