Q185085: FIX: Modal Form and Form with Treeview Causes Memory Error

Article: Q185085
Product(s): Microsoft FoxPro
Version(s): WINDOWS:5.0,5.0a
Operating System(s): 
Keyword(s): kbvfp
Last Modified: 23-MAR-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 5.0, 5.0a 
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SYMPTOMS
========

Adding nodes to a Treeview control that resides on an inactive page of a
pageframe after displaying a modal form, causes Visual FoxPro to generate one of
the error messages shown below.

In Windows NT 4.0, Dr. Watson for Windows NT reports the following error:

  An application error has occurred and an application log is being generated.
  VFP.exe
  Exception access violation(0xc00000050), Address: <memory address>

In Windows 95, the following error appears:

  This program caused and illegal operation and will be shutdown.

Pressing the Details button results in one of the messages below:

  VFP caused an invalid page fault in module <unknown> at
  <address>.

  -or-

  VFP caused an invalid page fault in module COMCTL32.OCX at <address>.

RESOLUTION
==========

Change the WindowType of the modal form to Normal. However, this allows users to
manipulate items that are not on the previously modal form.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This has been corrected in Visual FoxPro 6.0.

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

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

1. Create a form called Ztest and add a pageframe to the form.

2. Right-click the pageframe and choose Edit. Place a Microsoft TreeView control
  on each page and name them OLEControl1 and OLEControl2 respectively.

3. Place a command button on the form change the Caption property to Refresh.

4. In the Click event of the command button add the following code:

  

        * Refresh the first page of the pageframe.
        THISFORM.pageframe1.page1.OLEControl1.nodes.CLEAR
        FOR i= 1 TO 5
          THISFORM.pageframe1.page1.OLEControl1.nodes.ADD(,,,STR(RAND()*100))
          THISFORM.pageframe1.page1.OLEControl1.nodes.ADD(,,,STR(RAND()*100))
        ENDFOR
        * Refresh the second page of pageframe.
        THISFORM.pageframe1.page2.OLEControl2.nodes.CLEAR
        FOR i= 1 TO 5
          THISFORM.pageframe1.page2.OLEControl2.nodes.ADD(,,,STR(RAND()*100))
          THISFORM.pageframe1.page2.OLEControl2.nodes.ADD(,,,STR(RAND()*100))
        ENDFOR
        THISFORM.REFRESH

5. Add a second command button and change the Caption to "Do Modal Form."
  Add the following to the Click event of the command button:

  

        DO FORM modalform

6. Create a form called modalform, and change the Windowtype to 1-Modal. Add a
  command button to the form that has the following code in the Click event:

  

        ThisForm.Release

  Change the Caption property of the command button to Exit.

7. Save both forms.

8. Run the form using the following command:

  

        Do Ztest.scx

  Press the refresh button, and click the second page of the pageframe. Next,
  click the first page of the pageframe. Then, press the "Do Modal Form" button
  to call the modal form. Once the modal form appears, press the Exit button on
  the modal form. Finally, press the refresh button on Ztest.scx. The error
  occurs.

Additional query words: crash hang GPF kbvfp600fix

======================================================================
Keywords          : kbvfp 
Technology        : kbVFPsearch kbAudDeveloper kbVFP500 kbVFP500a
Version           : WINDOWS:5.0,5.0a
Issue type        : kbbug
Solution Type     : kbfix

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