Lambda帮助C#中的分组和求和，需要一个Func或表达式，小数>>

发布于 2024-09-11 05:18:19 字数 887 浏览 0 评论 0 原文

我在执行内联 .GroupBy() 和 .Sum() 操作时遇到一些麻烦。

我有通过 let 获得的数据子集，因此它的返回类型已经是匿名的。希望此示例中有足够的代码来展示我想要实现的目标...

from r in Repo.R
  join f in Repo.F
    on f.ID equals r.FFK

let totalB = Repo.B
    .Join(
        b => b.FKID,
        f => f.ID
        (b, f) => new { b.ID, b.Qty, b.Fee })
    .Where(
        b => b.someCriteria == someInput)

group r by new 
   { 
      r.Name,
      TotalFee = totalB
                 .GroupBy(tb => tb.TypeId)
                 .Sum(  /*having trouble here*/ )
   }
into rgroup
select new FinalOutput
   {
        rgroup.Key.Name,
        rgroup.Key.TotalFee
   }

我需要一个有效的：

Func<IGrouping<int, anonymous type>, int> selector

或

Expression<Func<IGrouping<int, anonymous type>, decimal>> selector

原文

I'm having a bit of trouble doing an inline .GroupBy() and .Sum() action.

I have a subset of data obtained via a let so it's return type is already anonymous. Hopefully there's enough code in this sample to show what I'm trying to achieve...

from r in Repo.R
  join f in Repo.F
    on f.ID equals r.FFK

let totalB = Repo.B
    .Join(
        b => b.FKID,
        f => f.ID
        (b, f) => new { b.ID, b.Qty, b.Fee })
    .Where(
        b => b.someCriteria == someInput)

group r by new 
   { 
      r.Name,
      TotalFee = totalB
                 .GroupBy(tb => tb.TypeId)
                 .Sum(  /*having trouble here*/ )
   }
into rgroup
select new FinalOutput
   {
        rgroup.Key.Name,
        rgroup.Key.TotalFee
   }

I need a valid:

Func<IGrouping<int, anonymous type>, int> selector

Expression<Func<IGrouping<int, anonymous type>, decimal>> selector

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初见 2024-09-18 05:18:31

您需要将分组传递到 Sum 选择器中，如下

.Sum(g => ...)

所示这里“g”是您的分组。它有一个键，它是分组所依据的值，并且它还包含您分组的所有值。这些是您的匿名类型的值。

如果您在“g”上调用 Sum，它将为您提供为匿名类型指定选择器的选项。

//this is how you can sum values within a grouping
.Sum(g => g.Sum(tb => tb.Fee))

在我的示例中，我猜测“Fee”是属性名称，但是一旦取消引用“tb”变量，您的智能感知就会启动并显示可用的属性。

我希望这有帮助:-)

You need to pass the grouping into the Sum selector like this

.Sum(g => ...)

Here "g" is your grouping. It has a key which is the value that it was grouped by, and it also contains all of the values that you grouped. These are values of your anonymous type.

If you call Sum on "g" it'll give you the option of specifying a selector for your anonymous type.

//this is how you can sum values within a grouping
.Sum(g => g.Sum(tb => tb.Fee))

I've guessed "Fee" as the property name in my example, but once you de-reference the "tb" variable your intellisense should kick in and show you the properties available.

I hope this helps :-)

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