protected override void OnRender(ChartControl chartControl, ChartScale chartScale)
{
  base.OnRender(chartControl, chartScale);
  // loop through only the rendered bars on the chart
  for(int barIndex = ChartBars.FromIndex; barIndex <= ChartBars.ToIndex; barIndex++)
  {
    // get the open price at the selected bar index value
    double openPrice = Bars.GetOpen(barIndex);
    Print("Bar #" + barIndex + " open price is " + openPrice);
  }
}