public override void AddValueChanged(object component, EventHandler handler) {
if (component == null) throw new ArgumentNullException("component");
if (handler == null) throw new ArgumentNullException("handler");
EventInfo changedEvent = ChangedEventValue;
if (changedEvent != null) {
changedEvent.AddEventHandler(component, handler);
}
else {
base.AddValueChanged(component, handler);
}
}