I should have thought of that, I guess thats what I get for making assumptions based on how I think windows components should behave...
Setter is not called when the textbox is cleared, which doesn't make any sense at all to me. I guess the BindingSource is doing a preliminary check on the type before attempting to write the value to the object...but who asked it to.
I guess I have a lot to learn about windows forms and databinding...Thanks for you patience and your help.