LINQ-to-SQL - 选择新内容中的'Sum'

Question

我有一个LINQ-to-SQL查询,它运行在一个表中,我想选择3个总和 - "Rate"和"AdditionalCharges"的总和,所以我有这样的事情:

var sums = from d in dc.Deliveries
where d.TripDate == DateTime.Now
select new
{
    Rate = d.Rate,
    AdditionalCharges = d.AdditionalCharges
};

但是,显然这会为每次传递返回一个新行,这意味着我必须在之后总结它们 - 这看起来效率很低.有没有更简单的方法？

Answer 1

我知道这是一个老问题,但是嘿,我找到了,所以希望这会帮助别人......

您也可以使用Fluent语法执行此操作:

var sums = dc.Deliveries
             .Where(d => d.TripDate == DateTime.Now)
             .GroupBy(d => d.TripDate)
             .Select(g =>
                 new
                 {
                     Rate = g.Sum(s => s.Rate),
                     AdditionalCharges = g.Sum(s => s.AdditionalCharges)
                 });

希望这有助于某人......

Answer 2

如果使用查询语法,则可以执行以下操作

var data = dc.Deliveries.Where(d => d.TripDate == DateTime.Now)
var rateSum = data.Sum(d => d.Rate);
var additionalCharges = data.Sum(d => d.AdditionalCharges);

这是我的头顶而没有经过测试

Answer 3

不确定,但你可以尝试下面的组再见功能

var sums = from d in dc.Deliveries
where d.TripDate == DateTime.Now
group d by new {d.Rate,d.AdditionalCharges,d.TripDate} into g
select new
{
    Rate = g.Sum(s => s.Rate ),
    AdditionalCharges = g.Sum(s => s.AdditionalCharges)
};