Exporting Grid view to excel,paging ,page size.

I have the gridview with dropdownfilters,sorting.
Every time i change the page size through page size dropdown,re-binding the grid.
And also during pageindex changing event re-binding the gridview.If i implement cutom paging,by passing pagno,page size (meam fetching the records from back end based on page no and pagesize.
What will happen when i export the grid to excel,will get only records belong to particualr page or all records.
I have to export the grid to excel at the same time performance should be good.
solution pls
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