小编Cur*_*man的帖子

protected void btnCalculateOrder_Click(object sender, EventArgs e)
{
    OrderSession();

    if (IsValid)
    {
        double RetailPrice = Convert.ToDouble(lblRetailPrice);
        double Quantity = Convert.ToDouble(txtQuantity);
        double Tax = (.9);

        double Subtotal = RetailPrice * Quantity;
        double TotalAmount = Subtotal + Tax;

        lblSubTotal.Text = Subtotal.ToString("c");
        lblTotalAmount.Text = TotalAmount.ToString("c");
    }

}