LINQ:如何在ObjectCollection中加入嵌套列表 [英] LINQ: How to join nested Lists in an ObjectCollection

问题描述

是否可以使用foreach循环为以下问题定义LINQ语句?

is it possible to define a LINQ statement for the following problems WITHOUT using a foreach loop?

public class GroupObject
{
    public String name;
    public List<String> letters;

    public void test()
    {
        List<GroupObject> myGroups = new List<GroupObject> {
            new GroupObject {
                name="test1",
                letters=new List<String>{"x","y","z"}
            },
            new GroupObject {
                name="test2",
                letters=new List<String>{"l","m","n"}
            },
            new GroupObject {
                name="test3",
                letters=new List<String>{"m","x","z"}
            }
        };

        // LINQ problem 1: how to get a list of all 9 letters
        // List<string> allLetters = (from ...).ToList();

        // LINQ problem 2: how to get a list of all 6 DISTINCT letters
        // List<string> allDistictLetters = (from ...).ToList();
    }
}

在撰写此问题时，我找到了解决问题的方法.我仍然会发布(并回答)这个问题，因为这个问题对我来说真是个麻烦.而且我在这里没有找到合适的现有问题.

While writing this question, I found a solution to the problems. I will still post (and answer) the question, since this one was a real bugger for me. And I did not find a suitable existing question here.

Ciao， 尤文

推荐答案

我相信SelectMany和Distinct可以解决此问题！

I believe this problem can be solved by SelectMany and Distinct!

var allLetters = myGroups.SelectMany(go => go.letters);
var allUniqueLetters = allLetters.Distinct();

第二个变量名称具有误导性.它将返回除其他字母外的"m"的一个实例，该实例在原始集合中不是 唯一；)

The second variable name is misleading tho. It will return, among other letters, one instance of "m", which was not unique in the original collection ;)

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