Fires when a backstage item is clicked.
The Click event's data class is EventArgs.
Handle the Click event to respond to a user clicking an item. If you want to define actions that are to be executed when a BackstageButtonItem is clicked, you can use either the Click event or bind a command to the button via the BackstageButtonItem.Command property. Handling the Click event for a BackstageTabItem doesn't prevent this tab item from being selected. To respond to a selection, use the BackstageViewControl.SelectedTabChanged event.