Private Sub btStartStopp_Click(ByVal sender As System.Object, _
         ByVal e As System.EventArgs) Handles btStartStopp.Click
 
        If stopwatch.IsRunning Then
            _elapsed = stopwatch.Elapsed
            timer1.Stop()
            Me.stopwatch.Stop()
 
            'Start-Uhrzeit und gemessenes Intervall notieren
            Dim se As String = _
                _starttime.ToString("F") & ";" & _elapsed.ToString("c")
            '... in Liste
            _measures.Add(se)
            '... Liste neu abrufen
            bsmeasures.ResetBindings(True)
            '... in Datei 
            IO.File.AppendAllText _
               ("C:\daten\measures.csv", se & Environment.NewLine)
 
            btStartStopp.Text = "Start"
            lblElapsed.Text = ""
            stopwatch.Reset()
        Else
            btStartStopp.Text = "Stop"
            _starttime = Date.Now
            timer1.Start()
            Me.stopwatch.Start()
        End If
    End Sub