Hi Mikhail,
Thanks for your interest in Syncfusion products.
Your requirement to page the data on demand can be achieved by setting IsPagingOnDemand to true and handling events “OnDemandDataSourceLoad“ and “OnDemandTotalRowCount”.
Please refer the below link for online sample.
http://asp.syncfusion.com/demos/ui/gridgrouping/Paging/OnDemandPaging/cs/OnDemandPaging.aspx Documentation Link
http://help.syncfusion.com/Ug_101/User%20Interface/ASP.NET/Grid/Documents/4102ondemandpaging.htm Please let us know if any concerns.
Regards,
Sridhar N