C#:从 IEnumerable<IEnumerable<T>> 获取不同的 T

Question

假设有一个对象IEnumerable<IEnumerable<T>> ，从该对象中获取不同 T 列表的最简洁方法是什么？

示例代码:

var listOfLists = new List<List<string>>();

listOfLists.Add(new string[] {"a", "b", "c", "c"}.ToList());
listOfLists.Add(new string[] {"a", "f", "g", "h"}.ToList());
listOfLists.Add(new string[] {"j", "k", "l"}.ToList());

List<string> distinctList = listOfLists.MagicCombinationOfEnumerableMethods();

Console.WriteLine(string.Join(", ", distinctList));

输出会是这样的:

a, b, c, f, g, h, j, k, l

Answer 1

你需要Enumerable.SelectMany

Projects each element of a sequence to an IEnumerable and flattens the resulting sequences into one sequence

List<string> distinctList = listOfLists.SelectMany(r => r).Distinct().ToList();

您还可以修改代码以在列表中添加元素，例如:

listOfLists.Add(new List<string> {"a", "b", "c", "c"});

而不是创建数组然后将其转换为列表。