| Title | Keep track of the number of MDI child forms |
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| Keywords | MDI, subforms |
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| Categories | Controls, Software Engineering |
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When an MDI child form loads or unloads, look through the Forms collection checking the MDIChild property.
The following code runs in a subform that may or may not be an MDI child form.
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Private Sub Form_Load()
MDIForm1.CountMDIChildren False
End Sub
Private Sub Form_Unload(Cancel As Integer)
MDIForm1.CountMDIChildren True
End Sub
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The following code runs in the MDI parent form named MDIForm1. Notice how it subtracts 1 from the MDI child form count if a child form is unloading. In that case, the child form is still in the Forms collection so it will be counted otherwise.
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Public Sub CountMDIChildren(ByVal one_leaving As Boolean)
Dim frm As Form
Dim is_child As Boolean
Dim num_mdi As Integer
For Each frm In Forms
' See if this form is an MDI child.
On Error Resume Next
is_child = frm.MDIChild
If Err.Number <> 0 Then is_child = False
On Error GoTo 0
If is_child Then num_mdi = num_mdi + 1
Next frm
If one_leaving Then num_mdi = num_mdi - 1
lblNumForms.Caption = Format$(num_mdi)
End Sub
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You can also simply have the child forms update a globally available counter variable when they load and unload.
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