GROUPBY在lambda表达式

本文介绍了GROUPBY在lambda表达式的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 from x in myCollection group x by x.Id into y select new { Id = y.Key, Quantity = y.Sum(x => x.Quantity) };

您会怎么写上面Lambda表达式？我卡上的组到部分。

How would you write the above as a lambda expression? I'm stuck on the group into part.

推荐答案

查询延续（SELECT ... INTO和组...成，但的不的加入...进入）等价于刚分手的查询表达式。所以我喜欢把你的例子为：通过X从X MyCollection中组X

Query continuations (select...into and group...into, but not join...into) are equivalent to just splitting up the query expression. So I like to think of your example as:

var tmp = from x in myCollection group x by x.Id; var result = from y in tmp select new { Id = y.Key, Quantity = y.Sum(x => x.Quantity) };

改变那些进入点符号：

Change those into dot notation:

var tmp = myCollection.GroupBy(x => x.Id); var result = tmp.Select(y => new { Id = y.Key, Quantity = y.Sum(x => x.Quantity) });

然后，你可以将它们合并回：

Then you could combine them back:

var tmp = myCollection.GroupBy(x => x.Id) .Select(y => new { Id = y.Key, Quantity = y.Sum(x => x.Quantity) });

一旦你制定出C＃编译器与查询表达式是什么，其余的是相对简单的：）

Once you work out what the C# compiler does with query expressions, the rest is relatively straightforward :)