public IVideoMedia CreateVideo(IInfoMedia infoMedia = null)
 {
     IVideoMedia media = new VideoMedia();
     if (infoMedia != null)
         infoMedia.SetInfo(media);
     return media;
 }
 public IImageMedia CreateImage(IInfoMedia infoMedia = null)
 {
     IImageMedia media = new ImageMedia();
     if (infoMedia != null)
         infoMedia.SetInfo(media);
     return media;
 }
 public IMusicMedia CreateMusic(IInfoMedia infoMedia = null)
 {
     IMusicMedia media = new MusicMedia();
     if (infoMedia != null)
         infoMedia.SetInfo(media);
     return media;
 }
 public void SetInfo(IInfoMedia infoMedia)
 {
     infoMedia.SetInfo(this);
 }