C#递归累计到父行

DataTable dt = new DataTable();
dt.Columns.Add("pid");
dt.Columns.Add("fatherid");
dt.Columns.Add("Categories");
dt.Columns.Add("Month");

 public DataTable SumNumber(DataTable dt, string fatherid)
        {
            //月累计
            double m_count = 0;

            //查询是否有下级
            DataRow[] rows = dt.Select("fatherid=‘" + fatherid + "‘");

            //上级变量,下级汇总数量到上级
            DataRow fatherow = null;
            if (dt.Select("pid=‘" + fatherid + "‘").Length > 0)
            {
                fatherow = dt.Select("pid=‘" + fatherid + "‘")[0];
            }

            //循环子行
            foreach (DataRow row in rows)
            {
                m_count = Convert.ToDouble(row["Month"]);
                //判断是否还有下下级
                DataRow[] childrows = dt.Select("fatherid=‘" + row["pid"] + "‘");
                foreach (DataRow item in childrows)
                {
                    SumNumber(dt, item["pid"].ToString());
                    m_count += Convert.ToDouble(item["Month"]);
                }
                //累计下下级到本级
                row["Month"] = m_count;
                //累计本级到上级
                if (fatherow != null)
                {
                    fatherow["Month"] = Convert.ToDouble(fatherow["Month"]) + m_count;
                }
            }

            return dt;
        }