Custom Validator

I'm using a custom validator but its event isn't firing if the value it's validating
is blank or just has spaces.

Is this legit behaviour?

In the meantime I guess I'll have to use a RequiredFieldValidator as well.

It does appear that I need to set-up multiple validators: one to check for
existance and another to check for correctness.

It also looks like the order of the validators is important. The Required one
should be declared before the Custom one...