递归算法 实现树结构

   string typelist = "";
    private string getnewstypetree(int id, int deep)
    {
        string deepstr = "－";
        string mydeepstr = "";
        for (int i = 0; i < deep; i++)
            mydeepstr += deepstr;
        string sql2 = "select id,newstype from news_type where upLevel_id=" + id + " order by id";
        DataSet ds = ukt.Select_Table_ReDS(sql2);
        if (ds.Tables[0].Rows.Count > 0)
        {
            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
            {
                typelist += "#" + ds.Tables[0].Rows[i][0].ToString() + "$" + mydeepstr + ds.Tables[0].Rows[i][1].ToString();
                getnewstypetree(int.Parse(ds.Tables[0].Rows[i][0].ToString()), deep + 1);
            }
        }
        return typelist;
    }