If I have understood you right, basically what you should do is:
1. Save the PageSize and the PageIndex of the dataPager.
2. Set the PageSize of the dataPager to 0.
3. Then export the data ((IEnumerable) dataPager.PagedSource ).
4. Set the PageSize and the PageIndex back.
I hope that this is what you need.
All the best,
the Telerik team
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