Here you can see an online example of a master-details implementation. This example follows the MVVM pattern and that is why we are using the collection called QueryableDataServiceCollectionView<T>. This is the same collection that the RDSDS control is internally using and is designed to be used in MVVM scenarios. The example could easily be re-worked to use two RDSDS controls instead of the two collections.
Let me know if you need further assistance.
All the best,
the Telerik team
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