Hi Ivan,
Sure - you have to create a const line attached to the Y axis:
NChart chart = nChartControl1.Charts[0];
NBarSeries bar = new NBarSeries();
bar.DataLabelStyle.Visible = false;
bar.Values.Add(17);
chart.Series.Add(bar);
NAxisConstLine constLine = new NAxisConstLine();
constLine.Value = 15;
constLine.StrokeStyle.Width = new NLength(2);
constLine.StrokeStyle.Color = Color.Red;
constLine.SetShowAtWall(ChartWallType.Back, true);
chart.Axis(StandardAxis.PrimaryY).ConstLines.Add(constLine);
Then you need to configure the legend in manual mode and it's done...
Best Regards,
Nevron Support Team