I've investigated this further. It appears to have nothing to do with the Mere Mortals framework, as I have reproduced the problems using a directly subclassed TextBox.

Near as I can tell, the Validating event just doesn't work as I would expect. Setting Cancel to true doesn't seem to stop anything from happening; all it does is restore the textbox to it's state before I typed anything after running through all its usual stuff. I cannot find a way to keep the changes in the textbox so I can fix a minor typo. Instead I have to retype the entire contents. Is this the way it is supposed to work?

...Jim