Hi Marina,
For the message you can use a NLabel object like this one:
NLabel label = new NLabel();
label.Text = "No data selected";
label.Location = new NPointL(new NLength(50, NRelativeUnit.ParentPercentage), new NLength(50, NRelativeUnit.ParentPercentage));
label.ContentAlignment = ContentAlignment.MiddleCenter;
label.Visible = false;
nChartControl1.Panels.Add(label);
When it happens that data does not exist you can clear the chart series, hide the axes and make the "no data" label visible:
chart.Series.Clear();
chart.Axis(StandardAxis.PrimaryY).Visible = false;
chart.Axis(StandardAxis.PrimaryX).Visible = false;
label.Visible = true;
Here we don't replace the whole chart, but simply clear some of its settings to make it look empty.
Best Regards,
Nevron Support Team