public void RemoveControlPageListener(System.Action <ControlPage> listener) { if (!OnPageActivation.GetInvocationList().Contains(listener)) { return; } OnPageActivation -= listener; }
public void AddControlPageListener(System.Action <ControlPage> listener) { if (OnPageActivation != null && OnPageActivation.GetInvocationList().Contains(listener)) { return; } OnPageActivation += listener; }