ASP.NET C# มัน error ครับ ช่วยดูให้หน่อยครับ งานเร่งครับ

<%@ Import Namespace="System.Data"%>
<%@ Import Namespace="System.Data.SqlClient"%>
<%@ Import Namespace="System.Web.UI.HtmlControls"%>
<%@ Import Namespace="System.Web.UI.WebControls"%>
<%@ Import Namespace="System.Web.UI.WebControls.WebParts"%>
<%@ Import Namespace="System"%>
<%@ Import Namespace="System.Collections"%>
<%@ Import Namespace="System.Configuration"%>
<%@ Import Namespace="System.Web.UI.WebControls.WebParts"%>
<%@ Import Namespace="System.Linq"%>
<%@ Import Namespace="System.Web"%>
<%@ Import Namespace="System.Web.Security"%>
<%@ Page Language="C#" Debug="true" %>

<script runat="server">
    
    SqlConnection objConn = new SqlConnection();
    SqlCommand objCmd = new SqlCommand();
    String strConnString;
    string term1, term_year1;
    DataSet ds = new DataSet();

    public void Page_Load(object sender, EventArgs e)
    {
            String strConnString;
            strConnString = "Server=MONOJA-PC\\SQLEXPRESS;UID=sa;PASSWORD=1234;database=mydatabases;Max Pool Size=400;Connect Timeout=600;";
            objConn = new SqlConnection(strConnString);
            objConn.Open();

            this.Button2.Enabled = false;
            BindData();
        
    }

    void BindData()
    {
        String sql_ct, sql_course, sql_teacher, sql_termyear, sql_term,sql_dc,sql_ct1;
        SqlDataReader dtReader, dtReader1,dtReader2;
        int intNumRows;
        sql_ct = "SELECT count(*) FROM course_teach where id_teacher='" + Session["id_teacher"] + "'";
        objCmd = new SqlCommand(sql_ct, objConn);
        intNumRows = Convert.ToInt32(objCmd.ExecuteScalar());

        if (intNumRows > 0)
        {
            sql_term = "SELECT term, term_year  FROM course order by term_year desc, term desc";
            objCmd = new SqlCommand(sql_term, objConn);
            dtReader = objCmd.ExecuteReader();
            dtReader.Read();
            string term = dtReader["term"].ToString();
            string termyear = dtReader["term_year"].ToString();
            this.lblTerm.Text = term;
            this.lblTerm_year.Text = termyear;
            dtReader.Close();
            dtReader = null;

            SqlConnection cnn = new SqlConnection("Server=MONOJA-PC\\SQLEXPRESS;UID=sa;PASSWORD=1234;database=mydatabases;Max Pool Size=400;Connect Timeout=600;");
            SqlDataAdapter cmd1 = new SqlDataAdapter("select distinct id_course,name_course,term,term_year from course where term='" + term + "' and term_year='" + termyear + "' order by term_year desc,term desc", cnn);

            
            cmd1.Fill(ds, "course");

            SqlDataAdapter cmd2 = new SqlDataAdapter("SELECT * FROM course_teach,course WHERE course.code_course=course_teach.code_course and course_teach.id_teacher = '" + Session["id_teacher"] + "'and course.term_year = '" + termyear + "' and course.term ='" + term + "' order by section", cnn);
            cmd2.Fill(ds, "course1");

            SqlDataAdapter cmd3 = new SqlDataAdapter("select * FROM style_test", cnn);
            cmd3.Fill(ds, "course2");

            //this.lb.Text = "select code_course,count(*) AS num FROM style_test WHERE code_course='1' group by code_course";
            ds.Relations.Add("myrelation",
            ds.Tables["course"].Columns["id_course"],
            ds.Tables["course1"].Columns["id_course"]);

            ds.Relations.Add("myrelation1",
            ds.Tables["course1"].Columns["code_course"],
            ds.Tables["course2"].Columns["code_course"]);

            parentRepeater.DataSource = ds.Tables["course"];
            Page.DataBind();
            cnn.Close();
            
        }
        else
        {
            Response.Write("<script type=\"text/javascript\">" + "alert('คุณยังไม่มีรายวิชา<br>กรุณาเพิ่มรายวิชา');" +
                "window.location = 'Create_course.aspx?id_teacher=" + Session["id_teacher"] + "';" + "</" + "script>");

        }
    }

    void Page_UnLoad()
    {
        objConn.Close();
        objConn = null;
    }

    void add_course(Object sender, EventArgs e)
    {
        Session["term"] = this.lblTerm.Text;
        Session["term_year"] = this.lblTerm_year.Text;
        Response.Redirect("Create_course1.aspx?id_teacher=" + Session["id_teacher"] + "&term=" + Session["term"] + "&term_year=" + Session["term_year"] + "");
    }

    protected void myRepeater_ItemDataBound(Object sender, RepeaterItemEventArgs e)
    {
        /*Label lblNum = (Label)(e.Item.FindControl("lblNum"));
        if (lblNum != null)
        {
            lblNum.Text = (string)DataBinder.Eval(e.Item.DataItem, "[\"num\"]");
        }*/
         
        HyperLink hplEdit = (HyperLink)(e.Item.FindControl("hplEdit"));
        if (hplEdit != null)
        {
            hplEdit.Text = "แก้ไข";
            hplEdit.NavigateUrl = "Edit_course.aspx?code_course=" + DataBinder.Eval(e.Item.DataItem, "[\"code_course\"]") + "&id_course=" + DataBinder.Eval(e.Item.DataItem, "[\"id_course\"]") + "&section=" + DataBinder.Eval(e.Item.DataItem, "[\"section\"]") + "&term=" + DataBinder.Eval(e.Item.DataItem, "[\"term\"]") + "&term_year=" + DataBinder.Eval(e.Item.DataItem, "[\"term_year\"]");
        }

        HyperLink hplExam = (HyperLink)(e.Item.FindControl("hplExam"));
        if (hplExam != null)
        {
            hplExam.Text = "จัดการสอบ";
            hplExam.NavigateUrl = "WebForm1.aspx?id_course=" + DataBinder.Eval(e.Item.DataItem, "[\"id_course\"]") + "&section=" + DataBinder.Eval(e.Item.DataItem, "[\"section\"]") + "&term=" + DataBinder.Eval(e.Item.DataItem, "[\"term\"]") + "&term_year=" + DataBinder.Eval(e.Item.DataItem, "[\"term_year\"]");
        }
    }

    void Back_course(Object sender, EventArgs e)
    {
        string id_teacher = Session["id_teacher"].ToString();
        Session["id_teacher"] = id_teacher;
        Session["term"] = this.lblTerm.Text;
        Session["term_year"] = this.lblTerm_year.Text;
        Response.Redirect("Back_course.aspx");
    }

    void Edit(Object sender, EventArgs e)
    {
        Response.Redirect("WebForm1.aspx?id_course="); 
    }
</script>

<html>
<head id="Head1" runat="server">
    <title>Untitled Page</title>
</head>
<body>
       
    <form id="form1" runat="server">
    
    <center>
    <asp:Label ID="lblDetial" runat="server" Text="รายวิชา" Font-Size="Larger" Font-Bold="true" />
<br />
        <asp:Button ID="Button1" runat="server" Text="Back" OnClick = "Back_course" />
        ภาคเรียนที่  <asp:Label ID="lblTerm" runat="server" /> / <asp:Label ID="lblTerm_year" runat="server" />
        <asp:Button ID="Button2" runat="server" Text="Next" />
    </center><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd /><dd />
    <asp:Button ID="btAdd_course" Text="เพิ่มรายวิชา" runat="server" OnClick="add_course"/> <br />
           
 <asp:repeater id="parentRepeater" runat="server">
 <HeaderTemplate><table border="1" align="center" width="30%"></HeaderTemplate>
   <itemtemplate>
   <tr><td>
      <b>รหัสวิชา <asp:Label ID="lblID_course" runat="server" ><%# DataBinder.Eval(Container.DataItem,"id_course") %></asp:Label>
      &nbsp;&nbsp; วิชา <%# DataBinder.Eval(Container.DataItem,"name_course") %>
      </b><br>

      <asp:repeater id="childRepeater" datasource='<%# ((DataRowView)Container.DataItem).Row.GetChildRows("myrelation") %>' OnItemDataBound="myRepeater_ItemDataBound" runat="server">
         <itemtemplate>
           <dd /> Section. <%# DataBinder.Eval(Container.DataItem, "[\"section\"]")%>
            <asp:repeater id="childRepeater1" datasource='<%# ((DataRowView)Container.DataItem).Row.GetChildRows("myrelation1") %>' runat="server">
         <itemtemplate>
           สอบทั้งหมด <%# DataBinder.Eval(Container.DataItem, "id_st")%>  ครั้ง  
           
            </itemtemplate>
      </asp:repeater>
             <asp:HyperLink ID="hplEdit" runat="server" />&nbsp;&nbsp;
             <asp:HyperLink ID="hplExam" runat="server" />

           <br>

         </itemtemplate>
      </asp:repeater>
      <br />
    </td></tr>
   </itemtemplate>
</asp:repeater> 
       <asp:Label ID="lb" runat="server" />
    </form>
</body>
</html>