public ActionResult Checkout(Payment Payment)
        {
            if (new CartBusiness { UserKey = Session.GetUserKey() }.GetCurrentCartCount() <= 0)
            {
                var ex = new HttpException(400, "");
                ex.Data["ErrType"] = Globals.ERRTYPES.CART_CARTEMPTY;
                throw ex;
            }
            var orderBusiness = new OrderBusiness();
            var currentOrder = orderBusiness.GetIncompleteOrder(Session.GetUserKey());
            if (currentOrder == null)
            {
                var ex = new HttpException(404, "");
                ex.Data["ErrType"] = Globals.ERRTYPES.ORDER_NOTFOUND;
                throw ex;
            }

            decimal ItemsTotal;
            decimal ShippingPrice;
            decimal OrderTotal;
            orderBusiness.CalculateOrderSummary(out ItemsTotal, out ShippingPrice, out OrderTotal, currentOrder);
            if (OrderTotal != Payment.AmountPaid)
            {
                var ex = new HttpException(400, "");
                ex.Data["ErrType"] = Globals.ERRTYPES.CHECKOUT_PAYMENTERROR;
                throw ex;
            }

            orderBusiness.Checkout(Payment, currentOrder);

            // order completed, SEND E-MAIL

            return RedirectToAction("CheckoutComplete", currentOrder);
        }