DOCUMENT:Q173351  03-SEP-1997  [vbwin]
TITLE   :BUG: Custom OCX Not Unloaded When Client Application Ends
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:WINDOWS:5.0
OPER/SYS:WINDOWS
KEYWORDS:vb5all

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

 - Microsoft Visual Basic Control Creation, Learning, Professional, and
   Enterprise Editions for Windows, version 5.0
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SYMPTOMS
========

If a variable is set to reference a UserControl or one of its constituent
controls in the InitProperties and ReadProperties events of the
UserControl, the reference is not released when the client application
ends; therefore, the OCX remains loaded. Because the OCX does not unload,
its Terminate event is not triggered when the application ends.

RESOLUTION
==========

You can work around this problem by using a variable that saves the Name
property of the control rather than an actual reference to the control. For
example, if you are using the following code in a UserControl in which the
Terminate event is not triggered:

     Dim o As Object

     Private Sub UserControl_InitProperties()
       Set o = Label1
     End Sub

     Private Sub UserControl_ReadProperties(PropBag As PropertyBag)
       Set o = Label2
     End Sub

replace the code with the following:

     Dim s As String

     Private Sub UserControl_InitProperties()
       s = Label1.Name
     End Sub

     Private Sub UserControl_ReadProperties(PropBag As PropertyBag)
       s = Label2.Name
     End Sub

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products
listed at the beginning of this article. We are researching this
bug and will post new information here in the Microsoft Knowledge
Base as it becomes available.

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

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

1. Start a new "ActiveX Control" project.

2. Add two Label controls to UserControl1.

3. Add the following code to UserControl1:

      Option Explicit

      Dim o As Object

      Private Sub UserControl_InitProperties()
         Set o = Label1
         MsgBox "InitProperties"
      End Sub

      Private Sub UserControl_ReadProperties(PropBag As PropertyBag)
          Set o = Label2
          MsgBox "ReadProperties"
      End Sub

      Private Sub UserControl_Terminate()
          MsgBox "Terminate"
      End Sub

4. Save the project and Make the OCX.

5. Start a new "Standard EXE" project.

6. Click Components on the Project menu. Check the custom OCX you
   built in step 4.

7. Add the custom control to Form1. Note that the InitProperties event
   fires as expected.

8. Press the F5 key to run the program. Note that the ReadProperties event
   fires. However, you would expect to receive a Terminate event and then
   the ReadProperties event.

9. Click End on the Run menu. Note that only ReadProperties fires, not
   Terminate and then ReadProperties as expected.

10. Exit the IDE. Note that the OCX now unloads and the Terminate events
    are triggered.
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Keywords          : vb5all
Version           : WINDOWS:5.0
Platform          : WINDOWS
Issue type        : kbbug

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

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Copyright Microsoft Corporation 1997.