Linq to Objects: TakeWhileOrFirst

Question

What would be the most readable way to apply the following to a sequence using linq:

TakeWhile elements are valid but always at least the first element

EDIT: I have updated the title, to be more precise. I'm sorry for any confusion, the answers below have definitely taught me something!

The expected behavior is this: Take while element are valid. If the result is an empty sequence, take the first element anyway.

Answer 1

I think this makes the intention quite clear:

things.TakeWhile(x => x.Whatever).DefaultIfEmpty(things.First());

My earlier, more verbose solution:

var query = things.TakeWhile(x => x.Whatever);
if (!query.Any()) { query = things.Take(1); }