C#求List中某个字段的和

循环遍历

 List<CancelCardEntity> cancelCardEntities = cancelCardFacade.SelectCancelCarduserIDLLL(cancelCardEntity);
              
                //查询退卡总金额

                for (int i = 0; i < cancelCardEntities.Count; i++) //循环遍历list中每一列的值
                {
                    sumCancelCard = cancelCardEntities[i].cancelCash + sumCancelCard; //将获得的值赋值给变量
                }

调用本身的方法

List<Entity.CancelcardEntity> list = selectCancelCard.selectCancelCard(dictionary);  //list 的返回值类型为实体层      
            if (list.Count==0)
            {
                return 0;
            }
            else
            {
                CancelCash = list.Sum(cancelCard => Convert.ToInt64(cancelCard.CancelCash));  //调用list本身的方法求和cancelCard为list的一个对象，可以改为其他值
                return CancelCash;
               
            }