When the datasource have 20 thousand rows of data,the speed to show it is so slow?How to improve the speed to show it?

[PEIYANG]

My code is radgridview.datasource=a   (a is list<studeng> whcih has 20 thousand ),the speed is so slow;
my idea is when user firstly enter the web page , I set  radgridview.datasource=a1 (a1 is the first 1 thousand rows of data in a);
and than I set radgridview.datasource=a1 (a1 is the first 2 thousand rows of data in a);
....
and than I set radgridview.datasource=a19 (a1 is the first 19 thousand rows of data in a);
 and than I set radgridview.datasource=a20 (a1 is the first 20 thousand rows of data in a);

but it seems doesn't work, how to solve it ?