Microsoft KB Archive/223099

Knowledge Base

FIX: DataMemberChanged Fails for UserControls

Article ID: 223099

Article Last Modified on 5/13/2003

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APPLIES TO

• Microsoft Visual Basic 6.0 Learning Edition
• Microsoft Visual Basic 6.0 Professional Edition
• Microsoft Visual Basic 6.0 Enterprise Edition

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This article was previously published under Q223099

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 that this is a bug in the Microsoft products that are 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:

194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

194295 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.

Keywords: kbbug kbfix kbctrl kbactivexevents kbvs600sp3fix KB223099

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