public HistoryMementoDeleteKeyframe(Metadata metadata, Guid keyframeId) { this.metadata = metadata; this.keyframeId = keyframeId; // TODO: save the complete keyframe to XML (including the thumbnail). // Including all drawings and trackable drawings associated with these drawings. Keyframe keyframe = metadata.GetKeyframe(keyframeId); if (keyframe == null) { throw new NullReferenceException("keyframe"); } data = KeyframeSerializer.SerializeMemento(metadata, keyframe); }