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Every developer needs any editbox where end-user can enter only numbers. This is very popular task and you may find a lot of such topics in the public forums/newsgroups.

But most answers in forums are incorrect as I see, because they suggest to write some code in OnKeyPress handler and to check there what is a character pressed.
I say that this code is an incorrect because user could enter any alfa-characters there anyway (via clipboard, for example).

Today I want to post a simple code that allow to solve this task without any problems.
Microsoft have the ES_NUMBER style for any editbox. So all what you need is to send this flag for your editbox:

var
  defstyle: dWord;
begin
  defstyle := GetWindowLong(Edit1.Handle, GWL_STYLE);
  SetWindowLong(Edit1.Handle, GWL_STYLE, defstyle or ES_NUMBER)
end;

If you also want to have a right aligned number, send additionally the ES_RIGHT flag there

It's all - only numeric characters are possible and this is controled on OS level. Hope that you'll like this tip...

Published: December 2, 2003

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