Q286241: PRB: Error Saving NULL Value w/ ADODC and Bound Controls

Article: Q286241
Product(s): Microsoft Visual Basic for Windows
Version(s): 2.5,2.5 SP1,2.6,6.0
Operating System(s): 
Keyword(s): kbDatabase kbGrpDSVBDB kbGrpDSMDAC kbDSupport kbmdac270
Last Modified: 23-AUG-2001

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
- Microsoft Data Access Components versions 2.5, 2.5 SP1, 2.6, 2.7 
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SYMPTOMS
========

When you use the ActiveX Data Object (ADO) Data Control with a text box that is
bound to certain data types, such as Integer or Date, you receive the following
error message:

  Operation was canceled.

The error message occurs when you move to a different record or update the
record.

CAUSE
=====

The data control is sending a NULL string to an ADO field that is defined as a
number or other non-character field.

RESOLUTION
==========

The following code demonstrates a workaround for the problem. In the WillMove
event of the ADO Data Control, set the DataChanged property of the text box to
False, and then assign the value NULL to the field:

  Private Sub Adodc1_WillMove(ByVal adReason As ADODB.EventReasonEnum, adStatus As ADODB.EventStatusEnum, ByVal pRecordset As ADODB.Recordset)

  If txtIntegerField.Text = "" Then
       If txtIntegerField.DataChanged Then
            txtIntegerField.DataChanged = False
            Adodc1.Recordset.Fields("IntegerField") = Null
       End If
  End If

  End Sub

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

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

1. In Visual Basic, create a new Standard EXE Project. Form1 is created by
  default.

2. On the Project menu, click Components, and then select Microsoft ADO
  DataControl 6.0 (OLE DB).

3. Add an ADO Data Control and two TextBox controls to Form1. ADODC1, Text1, and
  Text2 are created by default.

4. Connect the ADO Data Control to the Employees table in the Nwind.mdb database
  that comes with Visual Basic by setting the following property values:

  +--------------------------------------------------------------------------------------------------------------------------+
  | ConnectionString | Provider=Microsoft.Jet.OLEDB.4.0;Data Source=c:\Program Files\Microsoft Visual Studio\VB98\NWIND.MDB; | 
  +--------------------------------------------------------------------------------------------------------------------------+
  | RecordSource     | Employees                                                                                             | 
  +--------------------------------------------------------------------------------------------------------------------------+

5. Bind the Text1 TextBox control to the EmployeeID field of the Employees table
  by setting the following properties:

  +-------------------------+
  | DataSource | ADODC1     | 
  +-------------------------+
  | DataField  | EmployeeID | 
  +-------------------------+

6. Bind the Text2 TextBox control to the HireDate field of the Employees table
  by setting the following properties:

  +-----------------------+
  | DataSource | ADODC1   | 
  +-----------------------+
  | DataField  | HireDate | 
  +-----------------------+

7. Press the F5 key to run the test application, and then delete the value in
  the text box that contains the HireDate so that the text box is blank. When
  you attempt to move off the record, note that you receive the following error
  message:

  Operation was canceled.

8. Click OK to restore the original value.

9. Click the Close button (X) to stop the test application.

10. Open the Code window for the ADO Data Control, and paste the following code
  into the WillMove event procedure of the ADO Data Control:

     If Text2.Text = "" Then
       If Text2.DataChanged Then
            Text2.DataChanged = False
            Adodc1.Recordset.Fields("HireDate") = Null
       End If
  End If

11. Test the application again, and note that you can now delete the HireDate
  from the text box and reposition it without the error message occurring.

Additional query words:

======================================================================
Keywords          : kbDatabase kbGrpDSVBDB kbGrpDSMDAC kbDSupport kbmdac270 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600 kbMDACSearch kbMDAC250SP1 kbMDAC250 kbMDAC260 kbMDAC270
Version           : :2.5,2.5 SP1,2.6,6.0
Issue type        : kbprb

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