I strongly suggest that you examine this
help article which explains in detail how filtering in RadPivotGrid is done. As for saving the filtering settings you can do this by extracting the filter expressions from the FilterExpressions collection of the pivot and store them in your database. Later you can restore the settings in the Page_Load event.
IEnumerable<PivotGridGroupFilter> filterExpressions = RadPivotGrid1.FilterExpressions;
All the best,
the Telerik team
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