If the smart tag panel is currently hidden, the DesignerActionUIService.ShowUI(System.ComponentModel.IComponent) method will display the panel. This method raises the DesignerActionUIService.DesignerActionUIStateChange event, stipulating DesignerActionUIStateChangeType.Show as the event type.
The DesignerActionUIService.HideUI(System.ComponentModel.IComponent) and DesignerActionUIService.ShowUI(System.ComponentModel.IComponent) methods are implemented only to raise their corresponding events. The actual functionality is found in the handlers for these events, which are part of the design-time environment.