I am writing a WPF app and using the WPF Chart control. I have a custom tool class derived from NDragTool. In the MouseUp() handler, I'm trying to add a trend line to a chart control already populated with a data set. My code looks like this:

    var tradingChart = chartControl.Charts[0] as NCartesianChart;
    var newFreeTrendLine = new NTrendLine();
    newFreeTrendLine.BeginPoint = new NPointD(0.0f, 0.0f);
    newFreeTrendLine.EndPoint = new NPointD(100.0f, 100.0f);
    var trendLineStrokeStyle = new NStrokeStyle(10.0f, NColor.FromString("Blue"), LinePattern.Solid, 0, 1);
    newFreeTrendLine.StrokeStyle = trendLineStrokeStyle;
   if (tradingChart.Series.Count > 1)
    {
      tradingChart.Series.RemoveAt(0);
    }
    tradingChart.Series.Insert(0, newFreeTrendLine);
chartControl.Refresh();

I'm not seeing a trend line when I refresh. Can you tell me what I am doing wrong?