Hi Experts,
I have a NHeatMapSeries plot which looks like:

73% of original size (was 688x19) - Click to enlarge

I have added NAxisConstLines for the X-Axis in the following way:
   //--- Grid: Add constlines between single fields of HeatMap
    if (true) {
      for (int iX = (centerX * -1); iX < centerX; iX++) {
       NAxisConstLine oBoarderLine = chart.Axis(StandardAxis.PrimaryX).ConstLines.Add();
       oBoarderLine.StrokeStyle.Color = Color.SteelBlue;
       oBoarderLine.StrokeStyle.Width = new NLength(2.0f);
       oBoarderLine.FillStyle = new NColorFillStyle(new NArgbColor(255, Color.SteelBlue));
       oBoarderLine.Value = iX;
      }
    }

How can I bring these Lines to a topmost plot level so that they appear visible over the heatmap ?

Thanks for your help,
best regards,
joern