Getting keys from a Lookup

How do I get the collection of keys from a Loo开发者_JAVA技巧kup<> I created through the .ToLookup() method?

I have a lookup which maps int-values to groups of instances of a custom class. I need a collection of all the int keys that the lookup contains. Any way to do this, or do I have to collect and save them separately?

You can iterate through the set of key-item groups and read off the keys, e.g.

var keys = myLookup.Select(g => g.Key).ToList();

One fast way:

var myKeys = myLookup.Select(l=>l.Key);