Q194980: PRB: Form Close Fails if Control Bound to RDC is Dirty

Article: Q194980
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s): 
Keyword(s): kbCtrl kbVBp500 kbVBp600 kbGrpDSVBDB
Last Modified: 09-JAN-2000

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

A form cannot be closed or unloaded.

CAUSE
=====

If data in a control bound to a Microsoft RemoteData Control is changed and if
the RDC's underlying resultset is non-updateable, then attempts to close the
form will fail silently.

RESOLUTION
==========

One way to avoid this problem is to set the Enabled property of all controls
bound to an RDC to False. If edits are desired, then a command button to enable
the controls can be added to the form. The controls would be disabled when the
edit is committed or canceled.

Another way to avoid this problem is to add code similar to that below to the
Validate event procedure for each RDC:

     Private Sub MSRDC1_Validate(Action As Integer, Reserved As Integer)
         If Action = rdActionUnload Then
             If (MSRDC1.Resultset Is Nothing) Then
                 UndoEdits Me
             Else
                 If (Not MSRDC1.Resultset.Updatable) Then
                     UndoEdits Me
                 End If
             End If
         End If
     End Sub

Also add the following procedure to a standard module:

     Sub UndoEdits(frm As Form)
         Dim ctl As Control

         For Each ctl in frm.Controls
             On Error Resume Next
             If (TypeName(ctl.DataSource) = "MSRDC") Then
                 If (Err = 0) Then
                     ctl.DataChanged = False
                 ElseIf (Err <> 438) Then
                     MsgBox "Unexpected error!"
                     Stop
                 End If
             End If
         Next ctl
     End Sub

The effect of this code is to cause any changes to data to be ignored when the
form is being closed (rdActionUnload). It is assumed that this is the desired
behavior because the resultset is non-updateable. There are two pieces of this
code worth noting. If the RDC itself is not bound to data, then it is
"non-updateable" with respect to the behavior described in this article. Also,
error 438, "object does not support this property or method", will occur for any
controls that do not support a DataChanged property. Because this code checks
every control on the form, this error is expected for controls such as command
buttons.

If this problem is being encountered because the RDC's LockType property is set
to rdConcurReadOnly, then there is a simpler workaround than the above. Choose
another value for the LockType property, and add the following code to the RDC's
Validate event:

     If (Action = rdActionUpdate) Then Action = rdActionCancelUpdate

This problem can also be avoided by using the Microsoft ADO Data Control.

STATUS
======

Microsoft is researching this problem and will post new information here in the
Microsoft Knowledge Base as it becomes available.

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

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

1. Create a Standard EXE project in Visual Basic. Form1 is created by default.

2. To the default form, add a TextBox, a CommandButton, and a RemoteData
  Control.

3. Bind the RDC to some data source, and set the LockType property to
  rdConcurReadOnly.

4. Bind the text box to the RDC.

5. In the Click event of the CommandButton, set the Text property of the TextBox
  to some new value.

6. Try to close the form (e.g. click on the X button at the upper-right corner),
  and note that the form will not close. The workarounds are as indicated
  above.

Additional query words:

======================================================================
Keywords          : kbCtrl kbVBp500 kbVBp600 kbGrpDSVBDB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : WINDOWS:5.0,6.0
Issue type        : kbprb

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