How to enumerate over nested enumerators

I have a variable IEnumerable<IEnumerable<int>>. I'm trying to somehow aggregate it into an IEnumerable<int> which enumerates over all the integers in order. (All the integers from the first set, then all the integers from the 开发者_如何学编程second, etc.) I looked into LINQ's aggregate method, but the only examples I found was string concatenation, and I can't figure out how to apply it here.

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You're looking for the SelectMany which can be used to flatten nested IEnumerable<T> structures into an unnested IEnumerable<T>

IEnumerable<IEnumerable<int>> enumerable;
IEnumerable<int> flat = enumerable.SelectMany(x => x);