Occurs when the ShowNavigationItemController.ShowNavigationItemAction's selected item is about to change, to reflect the change of the active View.
The CustomUpdateSelectedItem event handler receives an argument of the DevExpress.ExpressApp.SystemModule.CustomUpdateSelectedItemEventArgs type.
This event is raised by the ShowNavigationItemController.UpdateSelectedItem method. Handle this event to perform specific actions when the ShowNavigationItemAction's selected item is about to change. You can perform the change of the selected item in a custom way. In this instance, set the event handler's CustomUpdateSelectedItemEventArgs.Handled parameter to true.