You can easily configure this by setting one of the widget's ContentViewDisplayMode property to be "Master" and the other - "Detail". This will automatically force the Master widget to stop url queries, and the Details widget will display nothing (or a single item in DetilsView, depending on how you configure it) until a URLquery is passed by the Master widget. I'm attaching a short video demonstrating how to set this functionality, please refer to it for more detailed information. If you have any additional questions, please let us know.
All the best,
the Telerik team
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