Please accept my apologies for not being clear enough in my previous post.
The correct way to prevent execution of a client-side event (that is cancelable) is to call set_cancel() method of the arguments object, e.g.:
Regarding the issue that you experience, I am not quite sure I understand the exact case. Creating a new folder does not trigger a postback. Do you have custom implementation of this functionality? If so, could you please provide a sample page demonstrating the issue so we can investigate it further?
All the best,
the Telerik team
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