PRB: "Invalid Property Value" When You Query MDIChild Property (190220)


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 Q190220

SYMPTOMS

In Visual Basic, if you query for the MDIChild property of an MDI Parent form, the following error occurs:
Error 380 : Invalid Property Value

CAUSE

MDI Parent forms do not have an MDIChild property. To query for this nonexistent property will result in the above error.

RESOLUTION

To resolve this, use the following code to query for the MDIChild property of a form:

Sample Code

   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

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

  1. Create a new Standard EXE project in Visual Basic.
  2. Add an MDI form to the project by selecting Add MDI Form from the Project menu.
  3. Set the MDIChild property of Form1 to True.
  4. Paste the following code in the General Declarations section of Form1: 
          Private Sub Form_Click()
         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
      End Sub
  5. Press F5 to run the project
  6. Click on Form1.
An error message displays "Run-Time Error 380 : Invalid Property Value" instead of printing all of the names of the forms, and a value indicating whether or not they are an MDI Child form
Modification Type:MajorLast Reviewed:5/12/2003
Keywords:kbcode kberrmsg kbprb KB190220
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