BUG: Unloading a Modal Form's Parent Form Causes VB To Hang (189812)


The information in this article applies to:

  • Microsoft Visual Basic Learning Edition for Windows 5.0
  • Microsoft Visual Basic Learning Edition for Windows 6.0
  • Microsoft Visual Basic Professional Edition for Windows 5.0
  • Microsoft Visual Basic Professional Edition for Windows 6.0
  • Microsoft Visual Basic Enterprise Edition for Windows 5.0
  • Microsoft Visual Basic Enterprise Edition for Windows 6.0
This article was previously published under Q189812

SYMPTOMS

In Visual Basic, if one form shows another form modally, and the second form tries to unload the first form in either its Unload or Query_Unload event, Visual Basic hangs.

CAUSE

When unloading a modal form's parent form, Visual Basic enters an infinite loop.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. We are researching this bug and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

Steps to Reproduce Behavior

  1. Create a new Standard EXE project in Visual Basic. Form1 is created by default.
  2. Add a new form (Form2) to the project.
  3. Add a CommandButton (Command1) to Form1 and add the following code to the Click Event: 
          Private Sub Command1_Click()
         Form2.Show vbModal
      End Sub
  4. Add a CommandButton (Command1) to Form2 and add the following code to Form2's code window: 
          Private Sub Command1_Click()
         Unload Me
      End Sub

      Private Sub Form_Unload(Cancel As Integer)
         Unload Form1
      End Sub
  5. Save and run the project.
  6. On Form1, click on Command1 to show Form2 modally.
  7. On Form2, click on Command1 to unload Form2, which unloads Form1 in its Unload event. Note that Visual Basic hangs. Use Task Manager to stop the non-responding application.
Modification Type:MajorLast Reviewed:5/13/2003
Keywords:kbbug KB189812
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