If e.CloseReason = CloseReason.UserClosing Then
            Dim result As MsgBoxResult
            result = MsgBox("Wollen Sie wirklich das Fenster schließen", _
              MsgBoxStyle.YesNo Or MsgBoxStyle.Question)
 
            If result = MsgBoxResult.Yes Then
                e.Cancel = False
            Else
                e.Cancel = True
            End If
        End If