Hi Rezza,
This behavior is by design - you can use the range series for this purpose:
NRangeSeries bar = new NRangeSeries();
bar.UseXValues = true;
bar.Values.Add(0);
bar.Y2Values.Add(10);
bar.XValues.Add(0);
bar.X2Values.Add(10);
bar.Values.Add(0);
bar.Y2Values.Add(30);
bar.XValues.Add(20);
bar.X2Values.Add(30);
chart.Series.Add(bar);
for example displays two bars that will change size when zoomed in or out.
Best Regards,
Nevron Support Team