用递归算法返回该元素id下面的所有子集id

        private List<int> listAreaId = new List<int>(); 
        /// <summary>
        /// 递归获取本区域下面的所有子集
        /// </summary>
        /// <param name="areaId"></param>
        private void GetAreaListId(int areaId)
        {
            string sql = string.Format(@"SELECT area_id FROM bi_area WHERE parent_id={0}", areaId);
            var dt = DBUtil.DiningBaseInfo.ADO.ExecuteDataTable(sql);
            if (dt != null && dt.Rows.Count > 0)
            {
                foreach (DataRow dr in dt.Rows)
                {
                    listAreaId.Add(Convert.ToInt32(dr["area_id"].ToString())); 
                    GetAreaListId(Convert.ToInt32(dr["area_id"].ToString()));
                }
            }
        }