Concatenate lists with LINQ

Question

Is it possible to concatenate a List<List<T>> into a List<T> with a single operation in a way which isn't horrible slow, i.e:

List<List<int>> listOfLists = new List<List<int>>();
List<int> concatenatedList = listOfLists.Something...

?

Answer 1

listOfLists.SelectMany( l => l );

full line:

List<int> concatenatedList = listOfLists.SelectMany( l => l ).ToList();

Answer 2

Something like this:

listOfLists.Aggregate(new int[0], (res, list) => res.Concat(list));