/// <summary>
        /// 向数据源添加评论索引实体对象及其对应的内容实体对象。
        /// </summary>
        /// <param name="dataFacade"></param>
        /// <param name="indexEntity">要添加的索引实体对象。</param>
        /// <param name="contentEntity">要添加的内容实体对象。</param>
        /// <returns></returns>
        /// <exception cref="ArgumentNullException">
        ///     <paramref name="indexEntity"/>为null
        ///     或
        ///     <paramref name="contentEntity"/>为null
        /// </exception>
        public static async Task AddPostComment(this IDataFacade dataFacade,
                                                CommentEntity indexEntity, CommentContentEntity contentEntity)
        {
            if (indexEntity == null)
            {
                throw new ArgumentNullException(nameof(indexEntity));
            }
            if (contentEntity == null)
            {
                throw new ArgumentNullException(nameof(contentEntity));
            }

            dataFacade.AddCommentIndexEntity(indexEntity);
            await dataFacade.CommitChanges();

            await dataFacade.AddCommentContentEntity(contentEntity);
        }