BUG: DBCombo Control Does Not Allow Selection on Modal Form

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic for Windows, 16-bit and 32-bit, version 4.0

SUMMARY

If a DBCombo control is placed on a form that is shown modally, then the user is unable to click a selection of the drop-down list. This behavior only occurs in an EXE file, it does not occur in the Design Environment of Visual Basic.

STATUS

Microsoft has confirmed this to be an issue in the Microsoft products listed at the beginning of this article. Microsoft is researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

WORKAROUND

To work around this problem, the function below can be used to simulate showing a form modally. The workaround allows the DBCombo control to be used.

Instead of showing a form modally, show the form using a method such as the one documented below. For example, to simulate invoking Form1 modally, call the method as shown below:

   ShowModalForm Form1

   Public Sub ShowModalForm(frmTarget As Form)
      Dim ofrm As Object
      'Disable all the forms
      For Each ofrm In Forms
        ofrm.Enabled = False
      Next ofrm

      'Now show the target form non-modal
      frmTarget.Show
      'If the frmTarget was disabled by the loop above
      'make sure it is now enabled
      frmTarget.Enabled = True

      'Sit in a loop until the target form is dismissed
      Do While frmTarget.Visible = True
      DoEvents
      Loop

      'We have left the loop, so the dialog has been dismissed
      'Now Enable the forms, and exit the procedure
      For Each ofrm In Forms
       ofrm.Enabled = True
      Next ofrm
   End Sub

Steps To Reproduce the Problem

1. Start a new project in Visual Basic. Form1 is created by default.

2. Insert a new form into the project by choosing Insert...Form.

3. On the new Form (Form2), place a Data control and a DBCombo control.

4. Set the Databasename property of the Data control to Biblio.mdb, found in the vb directory. Set the Recordsource property to Authors.

5. Set the RowSource property of the DBCombo control to Data1, and the ListField property of the DBCombo control to Author.

6. In the Click event for Form1, place the following code to invoke Form2 modally:

         Form2.Show vbModal
   

7. Compile an EXE by choosing File...Make EXE from the menu.

8. Using File Manager, or Windows Explorer invoke the EXE for the project.

9. Click Form1 so that Form2 is shown. Choose the drop-down list for the DBCombo control, and note that a selection of the list cannot be made.

   ShowModalForm Form2