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.
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:
Open a new Visual Basic Standard EXE project. Form1 is created by default.
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.
On the Project menu, click Components to display the Components dialog. Select Microsoft DataGrid control 6.0 (OLEDB) and click OK.
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.
Add a Label to UserControl1.
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
Close the UserControl design window. UserControl1 is now available in the toolbox.
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.
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
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.
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