extension method does is to apply all server operations(sorting/filtering/paging/grouping..etc.) over the data source and format the response returned to client grid object.
In order to implement server paging the response on read request should return paged data collection in Data
field and Total
field for the total count of items(so the pager can be properly build). ToDataSourceResult
does that for you.
Regarding the error you receive here are few possible solutions:
the Telerik team
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI