I have added custom code to update a tooltip as the user mouses over data points within a series, however the value for DataPointIndex is wrong unless I am also showing data labels, which is ugly and seems like bug.

private void ChartControl_OnMouseMove(object sender, MouseEventArgs e)
{
NHitTestResult hitTest = _ChartControl.HitTest(e.X, e.Y);

if (hitTest.ChartElement == ChartElement.DataPoint)
{
var tip = new SuperToolTip() { AllowHtmlText = DefaultBoolean.True };

if (hitTest.Series.Name != "Line Series" && hitTest.Series.Name != "Point Series")
{
var title = tip.Items.AddTitle(hitTest.Series.Name);
}

//title.Appearance.TextOptions.HAlignment = HorzAlignment.Center;

switch (hitTest.Series.GetSeriesType())
{
//case SeriesType.Line:
// {
// var series = (NLineSeries)hitTest.Series;
// break;
// }

case SeriesType.BoxAndWhiskers:
{
var series = (NBoxAndWhiskersSeries) hitTest.Series;
tip.Items.Add("Index: " + hitTest.DataPointIndex);
tip.Items.AddSeparator();
tip.Items.Add("Low: " + ((double)series.LowerBoxValues[hitTest.DataPointIndex]).ToString(Model.DataFormatString));
tip.Items.Add("High: " + ((double)series.UpperBoxValues[hitTest.DataPointIndex]).ToString(Model.DataFormatString));
tip.Items.Add("Mean: " + ((double)series.AverageValues[hitTest.DataPointIndex]).ToString(Model.DataFormatString));
tip.Items.Add("Median: " + ((double)series.MedianValues[hitTest.DataPointIndex]).ToString(Model.DataFormatString));

break;
}

default:
{
if (hitTest.Series is NSeries)
{
var series = hitTest.Series as NSeries;

tip.Items.Add("Value: " + ((double) series.Values[hitTest.DataPointIndex]).ToString(Model.DataFormatString));
}

break;
}
}

var showArgs = new ToolTipControllerShowEventArgs() { SuperTip = tip };

_ChartControl.Widget.KFrame.ToolTipController.ShowHint(showArgs);
}
else
{
_ChartControl.Widget.KFrame.ToolTipController.HideHint();
}

}