LINQ的：名单列出一个长长的清单 [英] Linq: List of lists to a long list

问题描述

我有类型的对象 A 它由键入 B 的对象的列表：

I've got an object of type A which consists of a list of objects of type B:

class A { list<B> Alist;}
class B { string C; string D;}

在我的节目，我有的对象：

In my program I have a list of A objects:

list<A> listOfA = computeAList();

和我想选择所有的 C 在该列表中的字符串。下面的语句我希望能给我我想要的结果;它返回一个包含 C 的名单列表：

and I would like to select all the C strings in that list. The following statement I hoped would give me the result I wanted; it returns a list of lists containing the C's:

var query = from objectA in listOfA
            select objectA.Alist.FindAll(x => x.C.Length > 0).C;

有没有办法让所有的 C 的呢？

推荐答案

YBO的回答将是我太第一反应。查询表达式相当于是这样的：

ybo's answer would have been my first response too. The query expression equivalent of this is:

var query = from a in computeAList()
            from b in a.Alist
            select b.C;

为了完整起见，在此线程的其他答案都在同一主题的变化。

For the sake of completeness, the other answers in this thread are variations on the same theme.

从YBO（完全相同的查询，表示为点表示）：

From ybo (the exact same query, expressed as dot notation):

var query = listOfA.SelectMany(a => a.Alist, (a, b) => b.C);

从雷·海斯（包括Where子句，我已经稍微重新格式化）：

From Ray Hayes (including the Where clause; I've reformatted slightly):

var query = listOfA.SelectMany(a => a.AList, (a, b) => b.C)
                   .Where(c => c.Length > 0);

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