I'm not sure I follow the question. If the ContentPane was the SelectedItem of the TabGroupPane then at the point at which you dragged it out and another pane became the SelectedItem of that TabGroupPane then the event does fire. The SelectionChanged of the TabGroupPane (which is defined by the base Selector WPF class) is simply an event raised when the SelectedItem changes so it would only be raised when a tab within that tabgroup is selected. It would not be affected by interactions with panes outside of the tabgroup if that's what you are asking. The ContentPanePlaceholder is only there as a placeholder should the pane's docked state be toggled such that it would be back in that location. If the pane's docked state is toggled then it would replace that placeholder. If the pane were instead dragged and docked somewhere else within the dockmanager then that placeholder would be removed since it would exist in a different container. If you need to know when a pane has the keyboard focus then you might use the GotKeyboardFocus WPF events or perhaps the PaneActivated.