The radopen() function is a client-side method of the RadWindowManager. Therefore the CustomClientDataViewRadWindow RadWIndow needs to be in the Windows collection of a RadWindowManager.
Please note that if no RadWindow with the required ID (the string passed as the second argument to the radopen() function) is found a generic one with the settings from the manager will be opened.
Please also note that the RadWindowManager is designed to work as a singleton - i.e. only one instance per page. The radopen (and radalert(), radconfirm(), radprompt() functions as well) are "taken" by the first manager that is created on the page, so if more than one is present you should first get a reference to it (via the $find() method, which usually requires the ClientID of the control, therefore requires server code blocks and therefore is difficult to use in an external JS file), then call its own open() method, as shown in this help article
. You can easily confirm if this is causing your issue by examining the source of the page and more precisely the $create() statement at the end.
the Telerik team
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