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

For the case when you do have a collection of collections, i.e. a List>, Enumerable.Aggregate is a more elegant way to combine all lists into one:

var combined = lists.Aggregate((acc, list) => { return acc.Concat(list); });