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Q244140: BUG: Visual Basic Application Using HtmlHelp API Crashes

Article: Q244140
Product(s): Microsoft Visual Basic for Windows
Version(s): 5.0,6.0
Operating System(s): 
Keyword(s): kbHTMLHelp kbVBp kbVBp500bug kbVBp600bug kbIDEProject kbGrpDSVB kbDSupport
Last Modified: 06-JUN-2002

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

A Visual Basic application that is running in the IDE uses the HtmlHelp function
to display a Help window. When the calling form is closed or the project is
stopped, a fatal error occurs. Under Microsoft Windows 95 and Microsoft Windows
98, the Visual Basic design environment shuts down with no message. Under
Microsoft Windows NT, an access violation occurs. Depending on the operating
system, an IPF or access violation occurs in a compiled program. These problems
do not occur on Windows 2000.

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. Start a new Visual Basic Standard EXE project. Form1 is created by default.

2. Add a CommandButton to Form1.

3. Add the following code to the General Declarations section of Form1:

  Option Explicit

  Private Declare Function HtmlHelp Lib "hhctrl.ocx" _
          Alias "HtmlHelpA" _
          (ByVal hwndCaller As Long, _
          ByVal pszFile As String, _
          ByVal uCommand As Long, _
          ByVal dwData As Long) _
          As Long

  Private Const HH_DISPLAY_TOPIC = &H0
  Private Const HH_CLOSE_ALL = &H12

  Private Sub Command1_Click()
     Call HtmlHelp(Me.hWnd, "IEXPLORE.CHM", _
                         HH_DISPLAY_TOPIC, 0)
  End Sub

  Private Sub Form_Unload(Cancel As Integer)
  '   Call HtmlHelp(Me.hWnd, "", HH_CLOSE_ALL, 0)
  End Sub

4. Run the project, and click Command1.

5. On Windows 95 and 98, Visual Basic closes. On Windows NT, you should see an
  access violation. If you build an executable, the application crashes when
  you close the form.

WORKAROUND
----------

Uncomment symbol the line of code in the Form_Unload event, and run the
application again. The problem will no longer occur.

NOTE: This problem does not occur on Windows 2000 or Windows XP.

Additional query words:

======================================================================
Keywords          : kbHTMLHelp kbVBp kbVBp500bug kbVBp600bug kbIDEProject kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : :5.0,6.0
Issue type        : kbbug
Solution Type     : kbpending

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

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