I have 20+ Textboxes on a form bound to data fields; some hold dates.  If an
invalid date is entered the control prevents the user from moving to another
control (this is automatically handled by the default implementation of
Textbox), but no error message is shown and nothing happens to alert the
user.  How can I alert the user to the error without writing code for each
Textbox.  DataGridView handles this nicely with a messagebox, but the only
solution I could find for Textbox was to write validation code for each
Textbox.  It doesn't seem like I should need to do this since the textbox
knows the data is invalid.  What am I missing?