I found it...

(chart.Axis(StandardAxis.PrimaryY)).Scale.RulerRange.Begin;
and
(chart.Axis(StandardAxis.PrimaryY)).Scale.RulerRange.End;

Anyway, thanks

NAxisScrollbarTool can be used to zoom in or out, which changes the scale tick labels.
After zooming in or out using the NAxisScrollbarTool, how to access the maximum and minimum values displayed on the y-axis scale.

Thanks in advance, so far the support from you guys has been excellent.