Hello Mark Davison,
Which client-side event are you handling with this code? One change we did make which might well be your problem is that when handling OnClientCommand of a command
(not the dock's OnClientCommand ) you pass two parameters, for example:
Until now sender was the command object itself, whereas we changed it to be the dock whose command has raised the event. If this is your case, then using sender.get_id(); instead of sender.get_RadDock().get_id(); should solve the problem. In case you have a different scenario, please provide more detailed information about it so we can help you as soon as possible.
All the best,
the Telerik team