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I am not absolutely sure what you mean by persisting the aggregate state on the RadGrid. Note that the aggregate is calculated based on the columns data. For instance if you have 10 items in your grid and you have a count aggregate on one of the columns, and after applying a filter which returns only 5 columns the aggregate will be change to this number. So basically the aggregate is not persisted, but it is calculated on runtime. As to a full list of the persisted controls and their properties you could check out the following help article
I hope this information helps.
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