LINQ to SQL-'；总和'；在select new中

本文关键字：select new 总和 to LINQ SQL- | 更新日期: 2023-09-27 17:58:30

我有一个LINQ to SQL查询，它运行在一个表中，我想选择3个sum，即"Rate"answers"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，很明显，这会为每次交付返回一个新行，这意味着我必须在之后对它们进行汇总——这似乎相当低效。有没有更简单的方法？

LINQ to SQL-'；总和'；在select new中

我知道这是一个老问题，但嘿，我找到了，所以希望这能帮助其他人。。。

您也可以使用Fluent语法：

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)
                 });

希望这能帮助到别人。。。

如果使用查询语法，可以执行以下

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

这是我的想法，没有测试

不确定，但您可以尝试以下中的分组再见功能

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)
};

您应该能够做到这一点：

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();

    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
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