sqldatareader使用不当会使网站出现异常

我使用的是三层开发这是业务逻辑层的代码  public static List<ApplyMd> GetApplyMdByID(int id)
    {
        List<ApplyMd> list = new List<ApplyMd>();
        try
        {
            SqlParameter[] spa ={
                new SqlParameter("@ID",SqlDbType.Int)
                               };
            spa[0].Value = id;
            SqlDataReader sdr = DBHelper.GetReader1("SELE_APPLYINFO_ID", spa);
            if (sdr.HasRows)
            {
                while (sdr.Read())
                {
                    ApplyMd applymd = new ApplyMd();
                    applymd.Appname = sdr["TITLE"].ToString();
                    applymd.Name = sdr["NAME"].ToString();
                    applymd.Egname = sdr["EGNAME"].ToString();
                    applymd.Age = Convert.ToInt32(sdr["AGE"].ToString());
                    //applymd.Ismarr = Convert.ToInt32(sdr["ISMARR"].ToString());
                    //applymd.Ismarrstr = sdr["ISMARR"].ToString();
                    applymd.Ismarr = Convert.ToBoolean(sdr["ISMARR"].ToString());                    applymd.Sex = sdr["SEX"].ToString();
                    applymd.Health = sdr["HEALTH"].ToString();
                    applymd.Her = sdr["HER"].ToString();
                    applymd.National = sdr["NATIONAL"].ToString();
                    applymd.Img = sdr["IMG"].ToString();                    applymd.Phone = sdr["PHONE"].ToString();
                    applymd.Email = sdr["EMAIL"].ToString();
                    applymd.Idcard = sdr["IDCARD"].ToString();
                    applymd.Hreaddr = sdr["HREADDRESS"].ToString();
                    applymd.Nowaddr = sdr["NOWADDRESS"].ToString();                    applymd.School = sdr["SCHOOLLE"].ToString();
                    applymd.Profes = sdr["PROFESSIONAL"].ToString();
                    applymd.Maxdeg = sdr["MAXDEGREE"].ToString();
                    applymd.Workdate = sdr["WORKDATE"].ToString();
                    applymd.Graduat = Convert.ToDateTime(sdr["GRADUATION"].ToString());                    applymd.Pclevel = sdr["PCLEVEL"].ToString();
                    applymd.Cantone = sdr["CANTONESELEV"].ToString();
                    applymd.Eglevel = sdr["EGLEVEL"].ToString();
                    applymd.Interest = sdr["INTEREST"].ToString();
                    applymd.Streng = sdr["STRENGTHS"].ToString();                    applymd.Objective = sdr["OBJECTIVE"].ToString();
                    applymd.Education = sdr["EDUCATIONEX"].ToString();
                    applymd.Workex = sdr["WORKEX"].ToString();
                    applymd.Memo = sdr["MEMO"].ToString();
                    applymd.Worksurl = sdr["WORKSURL"].ToString();                    applymd.Minsalary = sdr["MINSALARY"].ToString();
                    applymd.Salaryex = sdr["SALARYEX"].ToString();
                    applymd.Subdate = Convert.ToDateTime(sdr["SUBDATE"].ToString());                    
                    list.Add(applymd);
                }
                sdr.Close();
                sdr.Dispose();
            }        }
        catch (Exception ex)
        {
            Page page = (Page)HttpContext.Current.CurrentHandler;
            page.ClientScript.RegisterStartupScript(page.GetType(), "", "<script>alert('" + ex + "')</script>");        }
        finally
        {
            DBHelper.Connection.Close();
        }        return list;
    }
这是在aspx页面中的调用 int id = Convert.ToInt32(Request["ID"].ToString());
                //int id = 2;
                labe_job.Text = ApplyManager.GetApplyMdByID(id)[0].Appname.ToString();
                labe_name.Text = ApplyManager.GetApplyMdByID(id)[0].Name.ToString();
                labe_ename.Text = ApplyManager.GetApplyMdByID(id)[0].Egname.ToString();
                labe_age.Text = ApplyManager.GetApplyMdByID(id)[0].Age.ToString();                .........部分省略
                td_obje.InnerHtml = ApplyManager.GetApplyMdByID(id)[0].Objective.ToString();
                td_educ.InnerHtml = ApplyManager.GetApplyMdByID(id)[0].Education.ToString();
                td_workex.InnerHtml = ApplyManager.GetApplyMdByID(id)[0].Workex.ToString();
                td_memo.InnerHtml = ApplyManager.GetApplyMdByID(id)[0].Memo.ToString();                labe_minsal.Text = ApplyManager.GetApplyMdByID(id)[0].Minsalary.ToString();
                labe_salaryex.Text = ApplyManager.GetApplyMdByID(id)[0].Salaryex.ToString();
                labe_submdate.Text = ApplyManager.GetApplyMdByID(id)[0].Subdate.ToString();
而最近网站经常出现问题，老是打不开  不知道是哪里错了。