private static IObservable <Preview> LoadPreview(IPreviewLoader previewLoader, ReplyModel model) { if (model.PhotoData != null) { return(previewLoader.LoadPreview(model.PhotoData, PreviewQuality.Low)); } if (model.VideoData?.Thumbnail != null) { return(previewLoader.LoadPreview(model.VideoData.Thumbnail)); } if (model.StickerData?.Thumbnail != null) { return(previewLoader.LoadPreview(model.StickerData.Thumbnail)); } return(Observable.Empty <Preview>()); }