Inheritance: GalaSoft.MvvmLight.Messaging.MessageBase
            private void OnPageChange(PageChangeMessage obj)
            {
                if (_imageSources.ContainsKey(_currentPosition))
                {
                    var gifRenderer = ((GifRenderer)_imageSources[_currentPosition]);
                    if(gifRenderer.Visible)
                    {
                        gifRenderer.Visible = false;
                        _imageSources.Remove(_currentPosition);
                        RaisePropertyChanged("ImageSource");
                    }
                }

                if (!obj.Forward)
                {
                    Messenger.Default.Unregister<PageChangeMessage>(this);
                }
            }