(RadContextMenu only) The OnClientShowing client-side event occurs when the context menu is about to appear, either in response to a right-click on one of its targets or a call to the show method.
The OnClientShowing event does not occur when the context menu appears in response to a call its showAt method.
The event handler receives two parameters:
The instance of the context menu firing the event.
An eventArgs parameter containing the following methods:
get_targetElement returns a reference to the DOM element that was right-clicked to show the context menu. If the menu appeared in response to a call to the show method rather than a right-click on one of its targets, get_targetElement returns null.
get_domEvent returns a reference to the DOM event that caused the context menu to appear. If the context menu appeared because one of its targets was right-clicked, this is an event of type "contextmenu". If the context menu appeared because of a call to its show method, this is the DOM event that was passed as a parameter to the show method.
set_cancel lets you prevent the menu from appearing.
get_cancel returns a boolean value indicating whether the context menu will appear after the event handler exits.
You can use this event to initialize the context menu before it appears or to conditionally prevent the context menu from appearing: