- public event EventHandler<EventArgs> ThumbnailLoading;
- public event EventHandler<ThumbnailDoubleClickEventArgs> ThumbnailDoubleClick;
- public event EventHandler<ThumbnailImageSearchEventArgs> ThumbnailImageSearchClick;
+ public event EventHandler<EventArgs>? ThumbnailLoading;
+ public event EventHandler<ThumbnailDoubleClickEventArgs>? ThumbnailDoubleClick;
+ public event EventHandler<ThumbnailImageSearchEventArgs>? ThumbnailImageSearchClick;