I have an event handler for the Leave event of a text box, that checks that the user has entered an invalid value. It displays a message and tells the user that the value entered is wrong.
But here's the trouble: after if displays the message, it still allows the user to move on to another control. How do I force the focus back on that textbox so that the Leave event keeps invoking until the user gets it right?
Another thing. I'm still new to C#, and I would like to know if there is some way I can check the contents of that text box to make sure that are all alpha-numeric (ie, only "0123456789" allowed)