LINQ中的分组依据和和子句 [英] Group By and Sum clauses in LINQ

问题描述

我编写了一个简单的linq查询，如下所示:

I've written a simple linq query as follows:

var query = from c in context.ViewDeliveryClientActualStatus
            join b in context.Booking on c.Booking equals b.Id
            join bg in context.BookingGoods on c.Booking equals bg.BookingId
            select new { c, b, bg };

我已经用多个前提过滤了先前的查询，然后需要按一组字段分组并获取其中一些字段的总和，如下所示:

I have filtered the previous query with a number of premises and then needed to group by a set of fields and get the sum of some of them, as so:

var rows = from a in query
           group a by new {h = a.c.BookingRefex, b = a.c.ClientRefex, c = a.b.PickupCity, d = a.b.PickupPostalCode} into g
           select new
           {                     
               Booking_refex = g.Key.h,
               Client_refex = g.Key.b,
               //Local = g.
               Sum_Quan = g.Sum(p => p.bg.Quantity),
           };

我想从a中获取一些我未包含在group by子句中的值.我如何获得这些价值?无法通过g访问它们.

I'd like to get a few values from a which I haven't included in the group by clause. How can I get those values? They're not accessible through g.

推荐答案

您的LINQ表达式中的g是一个IEnumerable，其中包含具有额外属性Key的a's.如果要访问不属于Key的a字段，则必须执行某种聚合或选择.如果您知道该组中所有元素的特定字段都相同，则可以从组中的第一个元素中选择该字段的值.在此示例中，我假设c有一个名为Value的字段:

The g in your LINQ expression is an IEnumerable containing a's with an extra property Key. If you want to access fields of a that are not part of Key you will have to perform some sort of aggregation or selection. If you know that a particular field is the same for all elements in the group you can pick the value of the field from the first element in the group. In this example I assume that c has a field named Value:

var rows = from a in query
  group a by new {
    h = a.c.BookingRefex,
    b = a.c.ClientRefex,
    c = a.b.PickupCity,
    d = a.b.PickupPostalCode
  } into g
  select new { 
    BookingRefex = g.Key.h, 
    ClientRefex = g.Key.b, 
    SumQuantity = g.Sum(p => p.bg.Quantity),
    Value = g.First().c.Value
  }; 

但是，如果组中的c.Value相同，则最好将其包含在分组中，并使用g.Key.cValue进行访问.

However, if c.Value is the same within a group you might as well include it in the grouping and access it using g.Key.cValue.

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