/// <summary>
        /// 评论照片动态
        /// </summary>
        /// <param name="ActivityId"></param>
        /// <returns></returns>
        //[DonutOutputCache(CacheProfile = "Frequently")]
        public ActionResult _CommentPhoto(long ActivityId)
        {
            //实例化动态
            Activity activity = activityService.Get(ActivityId);

            if (activity == null)
            {
                return(Content(string.Empty));
            }
            ViewData["Activity"] = activity;

            //实例化评论
            PagingDataSet <Comment> commentPaging = commentService.GetRootComments(TenantTypeIds.Instance().Photo(), activity.ReferenceId, 1, SortBy_Comment.DateCreatedDesc);
            //去掉评论作者相同的评论然后取前3个
            IEnumerable <long> commentUserIds = commentPaging.AsEnumerable().Select(n => n.UserId).Distinct().Take(3);
            List <Comment>     commentList    = new List <Comment>();

            foreach (var commentUserId in commentUserIds)
            {
                commentList.Add(commentPaging.First(n => n.UserId == commentUserId));
            }
            IEnumerable <Comment> comments = commentList.AsEnumerable();

            if (comments == null)
            {
                return(Content(string.Empty));
            }
            ViewData["CommentCount"] = commentPaging.Count();

            //实例化照片
            Photo photo = photoService.GetPhoto(activity.ReferenceId);

            if (photo == null)
            {
                return(Content(string.Empty));
            }
            ViewData["Photo"] = photo;

            return(View(comments));
        }