Hi Irina,
You can switch the legend bounds mode to Fit in which which case it will resize in order to fill it's width or height of the panel associated with it - for example:
NLegend legend = nChartControl1.Legends[0];
legend.BoundsMode = Nevron.GraphicsCore.BoundsMode.Fit;
legend.UseAutomaticSize = false;
legend.Size = new Nevron.GraphicsCore.NSizeL(new NLength(20, NRelativeUnit.ParentPercentage), new NLength(20, NRelativeUnit.ParentPercentage));
Best Regards,
Nevron Support Team