WPF HitTest no longer available

Hello
We were using wpf version prior to 6, we just purchased new license and downloaded latest, but we found the HitTest api is gone, below is our code, it tries to figure out the line being clicked and get its data series.
Could you please let us know how to replace HitTest api?
Thanks

Sally

private void ChartPointClicked(object sender, MouseButtonEventArgs e)
{
e.Handled = true;

        Point mousePoint = e.GetPosition(Chart.GridLinesPanel as UIElement);
        double datapointRadius = 8;
        bool useInterpolation = false;
        HitTestInfo result;
        if (LineSeries.DataSeries != null)
            result = LineSeries.HitTest(mousePoint,datapointRadius, useInterpolation);
        else if (BoxSeries.DataSeries != null)
            result = BoxSeries.HitTest(mousePoint, datapointRadius, useInterpolation);
        else
            return;

        if (!result.IsHit)
            return;

        if (result.DataSeriesIndex <= Events.Count)
        {
            List<wExportEvent> runs = new List<wExportEvent>();
            runs = Events.Select(x => x.Wsdl).ToList();
            OpenRunSummary(runs, result.DataSeriesIndex);
        }
    }