public static decimal GetFinalPrice(Order order) { List <decimal> rebateprices = PromotionManager.GetActivePromotions() .Select(promo => PromotionManager.GetTotalRebatePrice(order, promo)) .ToList(); decimal origprice = order.Products.Sum(x => x.UnitPrice); decimal rebateprice = rebateprices.Sum(); return(origprice - rebateprice); }