BUG: Can't Check MDIChild Property of Forms in Forms Collection

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 5.0

SYMPTOMS

The following code worked in Visual Basic 4.0, but fails in Visual Basic 5.0 with an error "Error 380, Invalid Property Value" if an MDI parent form is in the project:

   Dim f As Form
   For Each f In Forms
      If f.MDIChild Then
         Form1.Print f.Name & "   MDI Child"
      Else
         Form1.Print f.Name & "   Not MDI Child"
      End If
   Next

CAUSE

MDI forms do not have an MDIChild property in either Visual Basic 4.0 or Visual Basic 5.0. Visual Basic 4.0 compensated for that in the specific case of looping through the forms collection and checking this property, but Visual Basic 5.0 does not.

RESOLUTION

The workaround is to determine if the form is an MDI form before checking the MDIChild property, which the following code demonstrates:

   Dim f As Form
   For Each f In Forms
     If Not TypeOf f Is MDIForm Then
       If f.MDIChild Then
         Form1.Print f.Name & "   MDI Child"
       Else
         Form1.Print f.Name & "   Not MDI Child"
       End If
     Else
       Form1.Print f.Name & "  Not MDI Child"
     End If
   Next

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.

Keywords          : vb5all kberrmsg
Version           : WINDOWS:5.0
Platform          : WINDOWS
Issue type        : kbbug