PRB: Error Message When You Save a NULL Value with ADODC and Bound Controls

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

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

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:

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.