Elegant way to combine multiple collections of elements?

Question

Say I have an arbitrary number of collections, each containing objects of the same type (for example, List foo and List bar).

Answer 1

You could always use Aggregate combined with Concat...

        var listOfLists = new List>
        {
            new List {1, 2, 3, 4},
            new List {5, 6, 7, 8},
            new List {9, 10}
        };

        IEnumerable combined = new List();
        combined = listOfLists.Aggregate(combined, (current, list) => current.Concat(list)).ToList();