上一篇文章,下一篇文章,搞不出来.该怎么解决

上一篇文章,下一篇文章,搞不出来.
网上找的一个方法,试了下不行的.

出来的结果,源代码: <a href=''></a>


news.aspx:

HTML code

上一篇:<a href='<%# preurl %>'><%# pretitle %></a>

C# code

        //上一篇,下一篇        protected void pre_next()        {            int now_id;            try            {                now_id = Convert.ToInt32(Request.QueryString["id"].ToString());            }            catch            {                now_id = 0;            }                        string pre_Sql = "select top 1 title,max(id) from news where id < now_id";                        string next_Sql = "select top 1 title,min(id) from news where id > now_id";            cn.Open();            SqlCommand cmd1 = new SqlCommand(pre_Sql, cn);            SqlDataReader sdr1 = cmd1.ExecuteReader();            if (sdr1.Read())            {                pretitle = sdr1["title"].ToString().Trim();                preurl = "Article.aspx?id=" + sdr1["id"].ToString() + " ";            }            else            {                pretitle = "第一篇了。";            }            cmd1.Dispose();            sdr1.Close();            SqlCommand cmd2 = new SqlCommand(next_Sql, cn);            SqlDataReader sdr2 = cmd2.ExecuteReader();            if (sdr2.Read())            {                nexttitle = sdr2["title"].ToString().Trim();                nexturl = "Article.aspx?id=" + sdr2["id"].ToString() + " ";            }            else            {                nexttitle = "最后一篇了";            }            sdr2.Close();            cmd2.Dispose();            cn.Close();        }