The filter/sort/group functionality is not platforms specific as it is part of the Telerik Report. The report viewers are only means to show Telerik Reports on the platform of your choice. If your inquiry is about doing this in code on the Silverlight client, the answer is you cannot as currently the report definition resides on the server. Introducing Silverlight report definition is in our plans for subsequent version of the product, but we cannot engage with a specific timeframe at this point.
All the best,
the Telerik team
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