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Q171487: FIX: Crash When Assigning Uninitialized Object to Tag

Article: Q171487
Product(s): Microsoft Visual Basic for Windows
Version(s): 5.0
Operating System(s): 
Keyword(s): kberrmsg kbVBp500 kbVS97sp2fix kbGrpDSVB kbvbp500sp2fix
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 5.0 
- Microsoft Visual Basic Professional Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 
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SYMPTOMS
========

Attempting to set the Tag property of one of the Windows Common Controls
(COMCTL32.OCX) at run-time may result in the following error and cause the
application to terminate:

  "VB5 caused an invalid page fault in module COMCTL32.OCX at 0137:202cb2a8."

CAUSE
=====

This problem occurs when the object variable that you are trying to assign to
the Tag property is uninitialized or is null.

RESOLUTION
==========

In Visual Basic 5.0, you can work around the problem by checking the value of
the variable before assigning it to the Tag property:

     Dim x As Object
     '...
     If x Is Nothing Then
        '
     Else
        StatusBar1.Panels(1).Tag = x
     End If

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been fixed in Visual Studio 97 Service
Pack 2.

For more information on the Visual Studio 97 Service Pack 2, please see the
following article in the Microsoft Knowledge Base:

  Q170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

For a list of the Visual Basic 5.0 bugs that were fixed in the Visual Studio 97
Service Pack 2, please see the following article in the Microsoft Knowledge
Base:

  Q171554 INFO: Visual Basic 5.0 Fixes in Visual Studio 97 Service Pack 2

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

With Visual Studio 97 Service Pack 2 installed, the above scenario correctly
yields with the following trappable run-time error.

  Run-time error '91':
  Object variable or With block not set.


Additional query words: listview toolbar treeview

======================================================================
Keywords          : kberrmsg kbVBp500 kbVS97sp2fix kbGrpDSVB kbvbp500sp2fix 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVBA500 kbVB500
Version           : 5.0
Issue type        : kbbug
Solution Type     : kbfix

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

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