Q180615: BUG: Text Box Value Does Not Change If ControlSource Is .NULL.

Article: Q180615
Product(s): Microsoft FoxPro
Version(s): MACINTOSH:3.0b; WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Operating System(s): 
Keyword(s): kbcode kbHWMAC kbvfp kbvfp500aBUG kbvfp500bug kbvfp600
Last Modified: 11-DEC-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0 
- Microsoft Visual FoxPro for Macintosh, version 3.0b 
-------------------------------------------------------------------------------

SYMPTOMS
========

When the ControlSource property of a text box control is set to the custom
property of a form and the custom property is .NULL., the text in the control
cannot be changed. If the text in the control is edited, the text changes to
.NULL. when the control loses focus.

RESOLUTION
==========

Change the class definition in the code below to add the KeyPress method as
follows:

     DEFINE CLASS NewTextBox AS textbox
        PROCEDURE KeyPress
        LPARAMETERS nKeyCode, nShiftAltCtrl
                *-- Once the text has changed, set the custom
                *-- property of the form to the text box.
           ThisForm.custom_prop = This.Value
        ENDPROC
     ENDDEFINE

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Create a program using the code below that creates a form with a custom
  property and two text boxes. The ControlSource of the first text box is set
  to the form's custom property.

        frmMain = CREATEOBJECT("frmBase")
        frmMain.Show
        READ EVENTS

        DEFINE CLASS frmBase AS Form

             *-- Set the property to a character type.
             custom_prop = ""

             PROCEDURE Init
                 ThisForm.custom_prop = .NULL.
             ENDPROC

             PROCEDURE Unload
           CLEAR EVENTS
        ENDPROC

            *-- Create the text box that gives the problem.
            ADD OBJECT text AS NewTextBox WITH ;
               Left = 100, ;
               Top = 0, ;
               Width = 250, ;
               Name = "txtText",;
               NullDisplay = ".NULL.",;
               ControlSource = "thisform.custom_prop"

           *-- Create another text box to give you something to tab into.
           ADD OBJECT text2 AS TextBox WITH ;
              Left = 100, ;
              Top = 50, ;
              Width = 250, ;
              Name = "txtText2"
        ENDDEFINE

        DEFINE CLASS NewTextBox AS textbox
        ENDDEFINE

2. Run the program and enter text into the first text box.

3. Tab to the next text box.

  The text in the control changes to .NULL.

Additional query words:

======================================================================
Keywords          : kbcode kbHWMAC kbvfp kbvfp500aBUG kbvfp500bug kbvfp600 
Technology        : kbHWMAC kbOSMAC kbVFPsearch kbAudDeveloper kbVFP300bMac kbVFP300 kbVFP300b kbVFP500 kbVFP600 kbVFP500a
Version           : MACINTOSH:3.0b; WINDOWS:3.0,3.0b,5.0,5.0a,6.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.