public static async Task <bool> IsSubscribedToAsync(this IIdentity identity, int noticeBoardId)
        {
            var id = identity.GetUserId();

            using (RelationshipManager rm = new RelationshipManager())
            {
                if (await rm.ExistsAsync(new UserNoticeBoardFollow {
                    NoticeBoardId = noticeBoardId, UserId = id
                }))
                {
                    return(true);
                }
                return(false);
            }
        }