We have an old method that used to search for a DataPoint and then display that position on the chart.  DataPoint is no longer found.  Has something changed about how data points are added.

Here's the code:

  private void OnValueChanged(object sender, EventArgs e)
   {
    var xAxisValue = DateTime.FromOADate(_chartHorizontalAxisCursor.Value);
    double yAxisValue = _chartVerticalAxisCursor.Value;
    NHitTestResult hitTest = _chartControl.HitTest(_mouseXPoint, _mouseYPoint);
    if (hitTest.ChartElement == ChartElement.DataPoint)
    {
      if (GetChartCategory(_resultsViewInfo.ChartType) == ChartCategory.Column)
      {
       toolTip1.SetToolTip(_chartControl, "Y:" + yAxisValue.ToString("N"));
      }
      else
      {
       toolTip1.SetToolTip(_chartControl, "X:" + xAxisValue.ToString("MMM dd hh:mm:ss tt") + ", Y:" + yAxisValue.ToString("N"));
      }
    }
    else
    {
      //toolTip1.SetToolTip(_chartControl, "JR");
      toolTip1.SetToolTip(_chartControl, "Y:" + yAxisValue.ToString("N"));
    }
   }