Concatenate lists with LINQ

Is it possibl开发者_如何转开发e 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...

?

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listOfLists.SelectMany( l => l );

full line:

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

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Something like this:

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