Quote:
Nothing is triggered. The message does not show.
Then the event handler is not correctly hooked up to the TextBox, or you are entering data in the wrong textbox (or wrong instance of the right textbox)
Start with the debugger: put a breakpoint on the first lien of the handler and check if it is hit. If it isn't, find every reference to the TextBox and put a breakpoint on all of those too. When you find out which reference isn't working as expected you can start fixing teh problem.
But we can't do any of that for you!