gtk-sharp 2.12.0.0 Gtk# is thread aware, but not thread safe; See the Gtk# Thread Programming for details. Event sender. Event arguments. Event handler. The event utilizes this delegate: Event data is passed via the parameter. To attach a to an event, add the WidgetEventHandler instance to the event. The methods referenced by the WidgetEventHandler instance are invoked whenever the event is raised, until the WidgetEventHandler is removed from the event. System.Delegate System.Void