Public Interface IChildWindowWithTab
        ReadOnly Property Name() As String
        Sub SetTabPageOnTabControl(TabName As String)
    End Interface
 
    Public Class AuftragBearbeiten
        Implements IChildWindowWithTab
 
        Public ReadOnly Property Name As String Implements _
          IChildWindowWithTab.Name
            Get
                Return MyBase.Name
            End Get
        End Property
 
        Public Sub SetTabPageOnTabControl(TabName As String) Implements _
          IChildWindowWithTab.SetTabPageOnTabControl
 
        End Sub
    End Class
 
    Public Class MainForm
        Public Function IsFormAlreadyLoaded2(FormToLoadName As String, _
          ParentName As Object, TabName As String) As Boolean
            Dim RueckgabeWert As Boolean = False
            For Each child As Form In ParentName.MdiChildren
                Dim childWindow As IChildWindowWithTab = TryCast(child, _
                  IChildWindowWithTab)
                If (childWindow IsNot Nothing) AndAlso (childWindow.Name = _
                FormToLoadName) Then
                    child.Activate()
                    child.BringToFront()
                    RueckgabeWert = True
                    If Not IsNothing(TabName) Then
                        childWindow.SetTabPageOnTabControl(TabName)
                    End If
                End If
            Next
            Return RueckgabeWert
        End Function
    End Class