c# - Elegant way to combine multiple collections of elements? -

say have arbitrary number of collections, each containing objects of same type (for example, list<int> foo , list<int> bar). if these collections in collection (e.g., of type list<list<int>>, use selectmany combine them 1 collection.

however, if these collections not in same collection, it's impression i'd have write method this:

public static ienumerable<t> combine<t>(params icollection<t>[] tocombine) {    return tocombine.selectmany(x => x); } 

which i'd call this:

var combined = combine(foo, bar); 

is there clean, elegant way combine (any number of) collections without having write utility method combine above? seems simple enough there should way in linq, perhaps not.

i think might looking linq's .concat()?

var combined = foo.concat(bar).concat(foobar).concat(...); 

alternatively, .union() remove duplicate elements.