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Q257787: FIX: Program w/ Usercontrol Causes Access Violation When Exiting

Article: Q257787
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): kbActiveX kbCtrl kbVBp600bug kbGrpDSVB kbDSupport kbVS600sp4fix kbVS600sp5fix
Last Modified: 27-JUL-2001

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
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SYMPTOMS
========

When an ActiveX control with two UserControl objects is created, one UserControl
acts as a data source and the other acts as a data consumer (bound to a data
source.) When another ActiveX control is created that includes the two preceding
UserControls and binds them together, a client program that uses the last
UserControl in the compiled program crashes with an Access Violation in
Msvbvm60.dll when it exits.

STATUS
======

Microsoft has confirmed that this is a bug in the Microsoft products that are
listed at the beginning of this article. This bug was corrected in the latest
service pack for Visual Studio 6.0.

For additional information about Visual Studio service packs, click the following
article numbers to view the articles in the Microsoft Knowledge Base:

  Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

  Q194295 HOWTO: Tell That a Visual Studio Service Pack Is Installed

To download the latest Visual Studio service pack, visit the following Microsoft
Web site:

  http://msdn.microsoft.com/vstudio/downloads/updates.asp

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

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

1. Start a Visual Basic ActiveX Control project. UserControl1 is created by
  default.

2. On the Project menu, choose References to open the References dialog box,
  check Microsoft ActiveX Data Objects 2.1 Library, and click OK.

3. Set the DataBindingBehavior property of UserControl1 to 1 - vbSimpleBound.

4. Add a TextBox control on UserControl1. Text1 is created by default.

5. Add the following code to the General Declarations section of UserControl1:

  Option Explicit

  Public Property Get Text() As Variant
    Text = Text1.Text
  End Property

  Public Property Let Text(ByVal New_Text As Variant)
    Text1.Text = New_Text
    PropertyChanged "Text"
  End Property

  ' Load property values from storage
  Private Sub UserControl_ReadProperties(PropBag As PropertyBag)
    Text1.Text = PropBag.ReadProperty("Text", Text1)
  End Sub

  ' Write property values to storage
  Private Sub UserControl_WriteProperties(PropBag As PropertyBag)

    Call PropBag.WriteProperty("Text", Text1.Text, Text1)
  End Sub

6. On the Tools menu, choose Procedure Attributes.

7. Set the contents of the Name combo box to Text.

8. Click the Advanced button, choose the following items, and click OK:

   - Property is data bound

   - This property binds to DataField

   - Show DataBindings collection at design time

   - Property will call CanPropertyChange before changing

   - Update immediate

9. On the Project menu, select Add User Control. UserControl2 is created by
  default.

10. Set the DataSourceBehavior Property of UserControl2 to 1 - vbDataSource.

11. Add a Shape control on UserControl2.

12. Add the following code to the General Declarations section of UserControl2.

NOTE: You need to change the path to Biblio.mdb in the UserControl_Initialize
event procedure if Visual Basic 6.0 is not installed on your C Drive.

  Option Explicit
  Dim TheConn As New ADODB.Connection
  Dim rs As ADODB.Recordset

  Private Sub UserControl_GetDataMember(DataMember As String, Data As Object)
    Set Data = rs
  End Sub

  Public Property Get Recordset() As Variant
    Recordset = rs
  End Property

  Private Sub UserControl_Initialize()
    Dim tmp As String
    
    tmp$ = "Provider=Microsoft.Jet.OLEDB.4.0;"
    tmp$ = tmp$ & "Data Source=C:\Program Files\Microsoft Visual " _
         & "Studio\VB98\BIBLIO.MDB;Persist Security Info=False"

    TheConn.ConnectionString = tmp$
    TheConn.Open
    Set rs = TheConn.Execute("select * from authors")
  End Sub

  Private Sub UserControl_Terminate()
    'On Error Resume Next
    
    On Error GoTo errHandler
    rs.Close
    TheConn.Close
    Exit Sub

  errHandler:
    MsgBox "Error in UserControl_Terminate" & Err.Number & "  " & Err.Description
  End Sub

  Public Sub MoveNext()
    If Not rs.EOF Then
      rs.MoveNext
    End If
  End Sub

  Public Sub MovePrevious()
    If Not rs.BOF Then
      rs.MovePrevious
    End If
  End Sub

  Public Sub MoveFirst()
    rs.MoveFirst
  End Sub

  Public Sub MoveLast()
    rs.MoveLast
  End Sub

13. On the File menu, choose Make Project1.ocx to compile the project.

14. On the File menu, choose Add Project to create an ActiveX control project.
  Project2 is added by default.

15. Change the Name property of UserControl1 in Project2 to UserControl3.

16. Add a UserControl1 on UserControl3. UserControl11 is added by default.

17. Place a UserControl2 on UserControl3. UserControl21 is added by default.

18. Set the following properties of UserControl11:

   - Set the DataSource property to UserControl21.

   - Set DataField property to Au_ID.

19. On the File menu, choose Make Project2.ocx to compile Project2.

20. On the File menu, choose Add Project to add a Standard EXE project. Project3
  is added by default.

21. Add UserControl3 on Form1 of Project3.

22. On the File menu, choose Make Project3.exe to compile the project.

23. Start Microsoft Windows Explorer, double-click Project3.exe, and note that
  Form1 is displayed.

24. Close Form1, and note that an Access Violation occurs.

Additional query words: sp4

======================================================================
Keywords          : kbActiveX kbCtrl kbVBp600bug kbGrpDSVB kbDSupport kbVS600sp4fix kbVS600sp5fix 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600
Version           : WINDOWS:6.0
Issue type        : kbbug
Solution Type     : kbfix

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