public void AddComment(CommentRegistrationPM commentRegistrationPM, UserIdentity userIdentity)
        {
            Notification notification    = null;
            var          comment         = commentRegistrationPM.GetComment();
            var          contentAuthorId = ContentBiz.Read(c => c.Id == comment.ContentId).Select(c => c.AuthorId).Single();

            comment.SenderId = userIdentity.UserId;
            CommentBiz.AddComment(comment);
            if (userIdentity.UserId != contentAuthorId)
            {
                notification = NotificationBiz.Add(NotificationType.WriteComment, userIdentity.UserId, comment.ContentId, contentAuthorId);
            }
            UnitOfWork.SaveChanges();
            commentRegistrationPM.Id         = comment.Id;
            commentRegistrationPM.CreateDate = comment.CreateDate;
            if (notification != null)
            {
                PushNotification.Send(contentAuthorId, PushNotificationType.NewNotification, NotificationBiz.ProcessNotification(notification).GetNotificationPM());
            }
        }