LINQ到SQL - '总结'内选择新

Question

我有一个LINQ到SQL查询运行通过一个表，我想选择3总和 - '汇率'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 
}; 

然而，显然这会返回一个新行，每交付，这意味着我必须在事后总结起来 - 这似乎是非常低效的。有更容易的方法吗？

Answer 1

如果您使用的查询语法，你可以这样做以下

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

这是关我的头顶，没有测试

Answer 2

不知道，但你可以尝试出组轮空功能如下

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 3

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 

Answer 4

我知道这是一个老问题，但嘿，我发现它，所以希望这将hel p别人......

你也可以做到这一点使用流利的语法：

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) 
       }); 

希望这可以帮助别人......

Answer 5

你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();