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，所以我有这样的东西：

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

然而，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 - 这似乎效率很低。有更简单的方法吗？

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);

这是我的头脑而未经过测试

Answer 3

不确定，但你可以尝试下面的分组再见功能

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)
};

Answer 4

你应该可以这样做：

DateTime d = DateTime.Now;
var sums = from d in dc.Deliveries
select new
{
    Rate = dc.Deliveries.Where(n => n.TripDate == d).Sum(n => n.Rate),
    AdditionalCharges = dc.Deliveries.Where(n => n.TripDate == d).Sum(n => n.AdditionalCharges)
};

var result = sums.FirstOrDefault();

Answer 5

    var sums = from d in dc.Deliveries
    where d.TripDate == DateTime.Now
    Group by d.TripDate // or primary key
    Into TotalRate = sum(d.Rate),
    TotalAdditionalCharges = sum(d.AdditionalCharges)
    Select TotalRate , TotalAdditionalCharges

LINQ-to-SQL - 选择新内容中的'Sum'

5 个答案: