Scott Mitchell put up a post about a CheckBoxList validator he built for ASP.NET 2.0. Worth checking out. I wrote a custom validator for CheckBoxLists a few weeks ago & while it wasn't too bad, I wish I had waited & just used Scott's. :) Also, he has some good tips about browser compatibility & RegisterExpandoAttribute.

FYI an expando attribute is an arbitrary attribute added to a HTML/DOM object at runtime. Weird name, I know.