KB176429 - BUG: Can't Check MDIChild Property of Forms in Forms Collection

Article ID: 176429

Article Last Modified on 5/12/2003

Microsoft Visual Basic 5.0 Learning Edition
Microsoft Visual Basic 6.0 Learning Edition
Microsoft Visual Basic 5.0 Professional Edition
Microsoft Visual Basic 6.0 Professional Edition
Microsoft Visual Basic 5.0 Enterprise Edition
Microsoft Visual Basic 6.0 Enterprise Edition

This article was previously published under Q176429

SYMPTOMS

The following code worked in Visual Basic 4.0, but fails in Visual Basic 5.0 or 6.0 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 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

CAUSE

MDI forms do not have a MDIChild property in Visual Basic 4.0, 5.0, or 6.0. 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 and 6.0 do 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: kberrmsg kbbug KB176429