Q223099: FIX: DataMemberChanged Fails for UserControls

Article: Q223099
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): kbservicepack kbActiveX kbActivexEvents kbCtrl kbVBp600bug kbGrpDSVB kbVS600sp2 kbVS600
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 6.0 
- 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
========

The DataMemberChanged method is used to notify data consumers that a data member
of a data source has changed, allowing the data consumers to refresh the data.
This method works correctly if called from a Class module. If this method is
called from a UserControl, no notification is sent and the data consumers are
unable to retrieve the new set of data.

CAUSE
=====

The parameter passed into the DataMemberChanged method is incorrectly
interpreted and the data consumers are not notified.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information
about Visual Studio service packs, please see the following articles in the
Microsoft Knowledge Base:

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

Q194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

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

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

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

2. On the Project menu, click References to display the References dialog.
  Select Microsoft ActiveX Data Objects 2.x Library and Microsoft Data Binding
  Collection and click OK.

3. On the Project menu, click Components to display the Components dialog.
  Select Microsoft DataGrid control 6.0 (OLEDB) and click OK.

4. On the Project menu, click Add User Control and then click Open to add a
  UserControl to your project. Resize the UserControl to make it smaller.
  Change the DataSourceBehavior property of the User Control to vbDataSource.

5. Add a Label to UserControl1.

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

  Private rs As ADODB.Recordset

  Public Sub changerecordset()
     
     Set rs = Nothing
     Set rs = New ADODB.Recordset
     
     rs.Fields.Append "field1", adBSTR, 25
     rs.Fields.Append "field2", adBSTR, 25
     rs.Fields.Append "field3", adBSTR, 25
     rs.Fields.Append "field4", adBSTR, 25
     rs.Open
     
     For i = 1 To 10
        rs.AddNew
        rs(0) = "a"
        rs(1) = "AA"
        rs(2) = "AAA"
        rs(3) = "AAAA"
        rs.Update
     Next i
     
     Call DataMemberChanged("foo")
     
  End Sub
     
  Private Sub Label1_Click()

  End Sub

  Private Sub UserControl_GetDataMember(DataMember As String, Data As Object)

     Set Data = rs
     
  End Sub

  Private Sub UserControl_Initialize()
     Label1.Caption = "My Data Control"
     Set rs = New ADODB.Recordset
     rs.Fields.Append "field1", adBSTR, 25
     rs.Fields.Append "field2", adBSTR, 25
     rs.Fields.Append "field3", adBSTR, 25
     rs.Fields.Append "field4", adBSTR, 25
     rs.Open
     
     For i = 1 To 10
        rs.AddNew
        rs(0) = CStr(i)
        rs(1) = CStr(i + i)
        rs(2) = CStr(i * i)
        rs(3) = CStr(i / i)
        rs.Update
     Next i
     
     DataMembers.Add "foo"
     
  End Sub

7. Close the UserControl design window. UserControl1 is now available in the
  toolbox.

8. Add a TextBox, a DataGrid control, two CommandButtons, and a UserControl1 to
  Form1. Resize the DataGrid to provide room for 10 rows and 4 columns.

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

  Private bc As BindingCollection
  Private Sub Command1_Click()

     Me.DataGrid1.DataMember = "foo"
     Set Me.DataGrid1.DataSource = Me.UserControl11
     
     Set bc = New BindingCollection
     bc.DataMember = "foo"
     Set bc.DataSource = Me.UserControl11
     bc.Add Text1, "text", "field1"
     
  End Sub

  Private Sub Command2_Click()

     Me.UserControl11.changerecordset

  End Sub

10. Run the project. Click Command1 to load values into the DataGrid control.
  Click Command2 and the values in the DataGrid do not change. The expectation
  is that updated values will be displayed. Click Command1 again to view the
  modified values. This demonstrates that the data do change when Command2 is
  clicked, but the DataGrid is not notified.

Additional query words:

======================================================================
Keywords          : kbservicepack kbActiveX kbActivexEvents kbCtrl kbVBp600bug kbGrpDSVB kbVS600sp2 kbVS600SP1 kbVS600sp3fix 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version           : WINDOWS:6.0
Issue type        : kbbug
Solution Type     : kbfix

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