Using Linq query inside List<T>.AddRange to conditionally add elements from one list to another

I have a List<String> and two List<CustomObject>.
I want to combine two List<CustomObject> but only if second List<CustomObject> property is not contained in List<String>.

So, want to do something like this:

resultSet1.AddRange(resultSet2.Select(x => !names.Contains(x.City)).ToList());

What am I missing here?