FIX: DataMemberChanged Fails for UserControls

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 6.0

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 kbGrpVB kbVS600sp2 kbVS600SP1 kbVS600sp3fix
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbbug