FIX: Crash When UserControl Accesses Members of ParentControls

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0

SYMPTOMS

When a UserControl tries to access members of the ParentControls collection when it is not in UserMode (AmbientProperties.UserMode = False), the following error may occur:

"VB5 caused an invalid page fault in module VB5.EXE at 0137:004650a3."

CAUSE

Visual Basic 5.0 is not releasing the interfaces correctly.

RESOLUTION

Install Visual Studio 97 Service Pack 2 (SP2). Alternately, use a For...Next loop instead of a For...Each loop when looping through the ParentControls collection to avoid the error.

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

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

MORE INFORMATION

Steps to Reproduce Behavior

1. Create a new Visual Basic 5.0 ActiveX Control project.



2. Add a Label control to the UserControl.



3. Add the following code to the UserControl:

   
         Public Property Let TheLoop(bLoop As Boolean)
            Dim oObject As Object
            Dim sName As String
            For Each oObject In ParentControls
                sName = oObject.Name
                Debug.Print sName
            Next
         End Property
   
         Public Property Get TheLoop() As Boolean
   
         End Property
    




4. Select File...Add Project from the menu bar and add a Standard EXE project.



5. Place an instance of UserControl1 (UserControl11) on Form1.



6. Place three or four other controls on Form1.



7. Select UserControl11 and change the TheLoop property.



8. Repeat step 7. Note that an invalid page fault in Visual Basic results.

Additional query words: kbDSupport

Keywords : kbVBp500 kbVS97sp2fix kbGrpVB kbvbp500sp2fix
Version : 5.0
Platform : WINDOWS
Issue type : kbbug