This is not possible, and it so by design. Besides text content, you can also add controls to the RadDock. If it is possible to set the text from the client, and persist the text on postbacks, then any client can modify the server content of the dock. This of course is a security breach in the server object of the RadDock control, which can result in unpredictable behavior of the page.
Greetings,
Pero
the Telerik team
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