Finally got these suckers working. You do need to define the control that needs to be validated before hand. After that it works like a charm. Probably the biggest time saving feature I’ve seen in .Net so far.
Been messing about with ASP.Net and was having trouble getting CustomValidators to work correctly. I wanted Server Side validation for a Username (check to make sure that the username does not exist). I got it to the point where it comes back if an error occurs without writing to the database but it didn’t display the error. Found this page: 4 Guys from Rolla that provided an easy server side only example. Still didn’t fix why my message wasn’t being displayed though. I think it has something to do with setting the controls to validate at design time in the design window. I am currently setting those properties at runtime through a function. Lets see how it goes when I switch that.