使用LINQ IEnumerable <IEnumerable <T >>到IEnumerable <T>

Question

如何将分裂IEnumerable的IEnumerables一个平坦的IEnumerable使用LINQ(或其他某种方式)？

Answer 1

enumerable.SelectMany(x => x)

Answer 2

var result = from e in enumerables
             from v in e
             select v;

Answer 3

IEnumerable<IEnumerable<int>> number_collections = ...
IEnumerable<int> = number_collections.SelectMany(x => x);