Hi,
My apologies for the delay in responding to you.
You can able to achieve your requirement using RepresentationType and ItemsSize property in chart web control.
The following code snippet exhibit how to set the size of the legend and how to change the default legend representation type in chart web control.
this.ChartWebControl1.Legend.ItemsSize = new Size(30, 30);
this.ChartWebControl1.Legend.RepresentationType = ChartLegendRepresentationType.Hexagon;
Please take alook at the attached sample.
http://websamples.syncfusion.com/samples/Chart.Web/5.1.0.51/F61420/main.htmLet me know if this helps.
Regards,
Rashidha.