递归实现无限级分类显示

string html = "";
    protected string GetClass(int ParentID,string TableName,string FileName)
    {
        SqlParameter sparm = new SqlParameter("@ParentID", SqlDbType.Int);
        sparm.Value = ParentID;
        SqlDataReader sdr = SqlHelper.ExecuteReader(SqlHelper.ConnectionString, CommandType.Text, "SELECT * FROM " + TableName + " WHERE ParentID = @ParentID ORDER BY ClassID ASC",sparm);
        if (sdr.HasRows)
        {
            html += "<ul>\n";
        }
        while (sdr.Read())
        {
            html += "<li><a href=\""+FileName+"?ClassID=" + sdr[0].ToString() + "\">" + sdr["ClassName"].ToString() + "</a>\n";
            if (Convert.ToInt16(sdr["Child"]) > 0)
            {
                GetClass(Convert.ToInt16(sdr["ClassID"]),TableName,FileName);   //如果有子分类则递归调用
            }
            html += "</li>\n";
        }
        if (sdr.HasRows)
        {
            html += "</ul>\n";
        }
        return html;
    }