Efficiently identifying if any item in first set matches any item in second set

I have two IEnumerable<string> that represent lists of strings. I want to see if any element in the first set matches any element in the second set. At the moment I have something that looks like this:

firstSet.Intersect(secondSet).Count() > 0

However, it seems to me to be rather inefficient because it will produce a list of the elements that match, then count them all. I can then test to 开发者_JAVA百科see if the count is greater than zero. I don't care about which match, how many match, just that any element in the two sets match. Is there anything like firstSet.AnyMatch(secondSet) that I'm missing?

Is there a more efficient way to express that?

Use Any instead:

if (firstSet.Intersect(secondSet).Any())

I believe this will build of hash set of the second collection first (in its entirety) and then iterate over the first set until it finds a match or runs out of elements to test. You may wish to bear this in mind when working out which way round to put firstSet and secondSet.

EDIT: Just to repeat what's already in a comment... if you know that (say) firstSet is a HashSet<string> then you should cast to it and use Overlaps:

HashSet<string> firstHashSet = (HashSet<string>) firstSet;
if (firstHashSet.Overlaps(secondSet))
{
    ...
}