Radgrid Sorts columns different then the Primary Key Column

[sweta]

Hello,

I'm using Radgrid version 2010.1.519.35. I have 10 columns in my radgrid which includes ID(PK), FirstName & LastName columns.
When i Select first time ID column it sorts the all the data in grid. I have Paging enabled grid. so when i sorts ID column it sorts for all pages. but if first time i sort FirstName or LastName then it sorts data only for current page. Please advise what i can do to resolve the issue.

Thanks
Sweta