public static void Show(string title, string message)
        {
            if (_popup != null)
            {
                return;
            }

            var root = Application.Current.RootVisual as PhoneApplicationFrame;            
            var notificationBox = new NotificationBox
            {
                Title = title,
                Message = message,
                Width = root.ActualWidth,
                MaxHeight = root.ActualHeight,
                HorizontalAlignment = HorizontalAlignment.Center,
                VerticalAlignment = VerticalAlignment.Center
            };

            if (!notificationBox.ShowAgain)
                return;
            
            _popup = new Popup
            {
                Child = notificationBox,
                IsOpen = true,                
            };
        }