Checking KeyPress is not the place to do your input validation

I have seen too many projects over the years trying to do input validation by checking KeyPress. This is not limited to Delphi projects (C#, VB and other projects suffer from this just as much). Most of these projects suffer from these::

• Much of the KeyPress logic logic in the UI byusing half-baked copy-pasted code fragments.
• They all fail missing important functionality (like paste, clear, Ctrl-key handling and such) either supporting or suppressing that functionality where needed

If doing Delphi, then that code should be rewritten in a generic way based on examples like like these:

• http://www.devsuperpage.com/search/Articles.asp?ArtID=857874 [WayBack]
• https://groups.google.com/forum/#!search/TNumberEdit$20Peter$20Below
  • https://groups.google.com/forum/#!search/TNumberEdit$20Peter$20Below/borland.public.delphi.vcl.components.using.general/vcH580PLBlg/E54-8UAdqKgJ [Archive.is]

–jeroen