TDateEdit
Delphi TEdit control with date and simple numeric validation.

This component is Freeware! Complete with source code.
It was written in Delphi 2, but you can recompile it for
whatever version you have, since the source is included.

Brought to you by:
Robert Manning
South Bay Computer Assistance
PO Box 21, Stanton, CA 90680
RobertM782@aol.com
76022.1630@compuserve.com

Description
===========
TDateEdit is a standard Delphi 2 TEdit control, with two new
boolean methods: IsValidDate and IsValidNumber.

Both methods return boolean true or false, to make writing it into
an expression very simple. For example, to check whether the
contents of the edit control is a valid date, you'd code:

if DateEdit1.IsValidDate then
begin
 {contents of DateEdit1 is a valid date, and you can safely use
  StrToDate on it, such as:}
  SomeTDateTimeField.AsDateTime := StrToDate(DateEdit1.Text);
end
else
 {contents of DateEdit1 is not a valid date, give user an
 error message if desired. the component will generate an error
 message for you, but does not generate an exception.} ;

How it works
============
The component will use your current settings in your Windows
environment for checking the date format. So, it is ok if you
are using M/D/Y, D/M/Y, or Y/M/D date formats (as set in the
ShortDateFormat global variable). The component will also use
the current DateSeparator character as defined in your Windows
environment. It will also properly check for February 29th in
leap years.

Numeric Validation
==================
Checking the DateEdit1 for a valid number is done the same way. It
will check for a valid Pascal-style number (positive or negative
integer or float only, scientific notation is not checked at this
time) so the contents may be safely converted with StrToFloat.

What I mean by Pascal style number is this: If a decimal point is
encountered, it must have a valid digit on either side of it. For
example, -1.0 or 0.99 is a valid Pascal-style number, but .9 is not.
Some languages let you get away with this, but not Pascal, so the
method will return false if the DateEdit control contains something
like (.9) or (1.)

I suggest converting the contents to a float, then using Round or
Trunc as desired to convert the value to an integer. I spent more
time being concerned with making this component check dates properly
than checking all possible number formats... so it can use some
improvement in this area. But for simple numbers it works fine.

Errors
======
The component will return a short error message if the date (or the
number) is invalid, but it *does not* generate an exception. Feel
free to remove these messages from the code if they're annoying,
or substitute with some other message.

Installation
============
Install the component in the usual way, it is set up to register
itself on the Samples component palette tab.

Author's Note
=============
Please let me know if you have any trouble using this component. As
usual, with a free component, no guarantee or warranty is expressed or
implied, blah blah blah ;-) But please let me know if something goes
wrong, or if you have suggestions.

You also have my permission to use this component in any way you
want, including recoding it. If you do happen to improve the coding,
I would appreciate a copy of the new unit ;-)

Enjoy!

Robert Manning
South Bay Computer Assistance
PO Box 21, Stanton CA 90680 USA
RobertM782@aol.com, 76022.1630@compuserve.com
http://members.aol.com/robertm782/public/sbcapage.htm