public decimal CheckoutCart(CartDTO cartViewModelObj) { decimal totalBillAmount = 0; if (cartViewModelObj != null && cartViewModelObj.CartItems != null && cartViewModelObj.CartItems.Count > 0) { var promotionCodes = promotionObj.GetActivePromotionCode(); totalBillAmount = promotionObj.ApplyPromotionCode(cartViewModelObj.CartItems, promotionCodes); } return(totalBillAmount); }