Occurs when the Document is closing. All components that listen to events from the document must also listen to this event with handlers that only adds close actions using AddCloseAction(ClosingEventArgs T  CloseAction). The typical responsibility of a close action is to tear down views of the document, which includes disposing ExternalEventManagers.

public event EventHandler<ClosingEventArgs<Document>> DocumentClosing

public event EventHandler<ClosingEventArgs<Document>> DocumentClosing