Private Delegate Sub del_prop_changed(sender As Object, e As System.ComponentModel.PropertyChangedEventArgs)

Sub prop_changed(sender As Object, e As System.ComponentModel.PropertyChangedEventArgs)
If tab1.Dispatcher.CheckAccess = False Then
   Dim del As New del_prop_changed(AddressOf prop_changed)
   tab1.Dispatcher.Invoke(del, sender, e)
End If
If Me.tab1.IsSelected = False Then Me.tab1.IsSelected = True
end sub