如何写一个LINQ查询通过聚集和组合组？ [英] How to write a LINQ query combining group by and aggregates?

问题描述

由于以下输入，我怎么写LINQ查询或前pression返回聚集结果的数量设置？

Given the following input, how do I write a LINQ query or expression to return an aggregated result set for the quantity?

输入：

var foo = new[] { new { PO = "1", Line = 2, QTY = 0.5000 }, 
                  new { PO = "1", Line = 2, QTY = 0.2500 }, 
                  new { PO = "1", Line = 2, QTY = 0.1000 }, 
                  new { PO = "1", Line = 2, QTY = -0.1000 } 
                }.ToList();

期望的结果：

Desired result:

沿东西线

new { PO = "1", Line = 2, QTY = 0.7500 } // .5 + .25 + .1 + -.1

如何将我写的多条线路，以及（见FOO对象模型）？

How would I write it for multiple lines as well (see the object model in foo)?

推荐答案

这个怎么样：

var result = foo.GroupBy(x => x.Line)
                .Select(g => new { PO = g.First().PO, 
                                   Line = g.Key, 
                                   QTY = g.Sum(x => x.QTY) });

在这种情况下，你只是有一个线，只需添加一个。单（） - 结果是的IEnumerable 在设置中定义的匿名类型的富。

In the case you just have one Line, just add a .Single() - result is an IEnumerable of the anonymous type defined when you set up foo.

编辑：

如果双方PO和线路应指定不同的组（PO可以有不同的值），它们都必须是组密钥的一部分：

If both PO and Line should designate different groups (PO can have different values), they both have to be part of the group key:

var result = foo.GroupBy(x => new { x.PO, x.Line})
                .Select(g => new { 
                    PO = g.Key.PO, 
                    Line = g.Key.Line, 
                    QTY = g.Sum(x => x.QTY) 
                  });

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