ASP.NET

<telerik:RadAsyncUpload ID="FileUpload1" runat="server" Skin="Forest" Width="272px">
</telerik:RadAsyncUpload>

<asp:Button ID="btnUpload" Width="180px"  Height="30px" runat="server" Text="Upload"
                           onclick="btnUpload_Click" />

<telerik:AjaxSetting AjaxControlID="btnUpload">
    <UpdatedControls>
          <telerik:AjaxUpdatedControl ControlID="btnUpload" LoadingPanelID="RadAjaxLoadingPanel1"></telerik:AjaxUpdatedControl>
     
        <telerik:AjaxUpdatedControl ControlID="FileUpload1" LoadingPanelID="RadAjaxLoadingPanel1"></telerik:AjaxUpdatedControl>
         
        <telerik:AjaxUpdatedControl ControlID="lblMessage" LoadingPanelID="RadAjaxLoadingPanel1"></telerik:AjaxUpdatedControl>
 
    </UpdatedControls>
</telerik:AjaxSetting>

    <telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" runat="server">
    </telerik:RadAjaxLoadingPanel>

Uncaught TypeError: Cannot read property 'id' of undefined Telerik.Web.UI.WebResource.axd:2889
Telerik.Web.UI.RadAjaxControl._initializeRequest Telerik.Web.UI.WebResource.axd:2889
H.z.callBaseMethod Telerik.Web.UI.WebResource.axd:3
Telerik.Web.UI.RadAjaxManager._initializeRequest Telerik.Web.UI.WebResource.axd:3463
(anonymous function) Telerik.Web.UI.WebResource.axd:3
(anonymous function) Telerik.Web.UI.WebResource.axd:3
H.w.raiseEvent Telerik.Web.UI.WebResource.axd:3
e._onFormSubmit Telerik.Web.UI.WebResource.axd:9
e._doPostBack Telerik.Web.UI.WebResource.axd:9
(anonymous function) Telerik.Web.UI.WebResource.axd:3
onclick

<ajax:ModalPopupExtender ID="mpePopup" runat="server"
       TargetControlID="btnPopupTargetControl"
       PopupControlID="pnlPopup"
       OkControlID="btnPopupOKControl"
       PopupDragHandleControlID="divPopup"
       BackgroundCssClass="modalBackground"
       DropShadow="true"
       RepositionMode="RepositionOnWindowResizeAndScroll"
       >
       <Animations>
           <OnShowing>
               <FadeIn Duration=".5" Fps="30" />
           </OnShowing>
           <OnShown>
               <FadeIn Duration=".5" Fps="30" />
           </OnShown>
           <OnHiding>
               <FadeOut Duration=".5" Fps="30" />
           </OnHiding>
           <OnHidden>
               <FadeOut Duration=".5" Fps="30" />
           </OnHidden>
       </Animations>
   </ajax:ModalPopupExtender>

System.Security.Principal.WindowsIdentity.GetCurrent().Name;

NT AUTHORITY\IUSR

<identity impersonate="true"/>
   <authentication mode="Windows" />
   <authorization>
     <allow users ="*" /><!-- This allows access to all users -->
   </authorization>

using System;
using System.Data;
using System.Data.OleDb;
using System.Web.UI.WebControls;

public partial class frmRegisterStudent : System.Web.UI.Page
{
    private void PopClass()
    {
        // Populate Class and add Please Select
        // Populate Student and add Please Select
        string path = Server.MapPath("eAcademy_DB.mdb");
        string connectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source=" + path;
        string commandText10 = "SELECT class_ID FROM tblClass WHERE class_ID NOT IN (SELECT class_ID FROM tblschedule GROUP BY class_ID HAVING COUNT(class_ID) >= 10)";

        var ds10 = new DataSet();

        using (var connection10 = new OleDbConnection(connectionString))
        using (var command = new OleDbCommand(commandText10, connection10))
        {
            // OleDbCommand uses positional, rather than named, parameters.
            // The parameter name doesn't matter; only the position.
            command.Parameters.AddWithValue("@p0", ddlstudID.SelectedValue);

            var adapter = new OleDbDataAdapter(command);
            adapter.Fill(ds10);
        }

        ddlclassSelect.DataSource = ds10;
        ddlclassSelect.DataTextField = "class_ID";
        ddlclassSelect.DataValueField = "class_ID";
        ddlclassSelect.DataBind();
        ddlclassSelect.Items.Insert(0, new ListItem("Please Select", "0"));
                      
            
    }
    private void PopStud()
    {
        // Populate Student and add Please Select
        string path = Server.MapPath("eAcademy_DB.mdb");
        string connectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source=" + path;
        //string commandText = "SELECT * from tblStudent";
        string commandText = "SELECT * FROM tblStudent where tblStudent.stud_id in (SELECT tblSchedule.stud_id FROM tblSchedule GROUP BY tblSchedule.stud_id HAVING count(tblSchedule.stud_ID) < 3)";
        var ds9 = new DataSet();

        using (var connection9 = new OleDbConnection(connectionString))
        using (var command = new OleDbCommand(commandText, connection9))
        {
            // OleDbCommand uses positional, rather than named, parameters.
            // The parameter name doesn't matter; only the position.
            command.Parameters.AddWithValue("@p0", ddlstudID.SelectedValue);

            var adapter = new OleDbDataAdapter(command);
            adapter.Fill(ds9);
        }

        ddlstudID.DataSource = ds9;
        ddlstudID.DataTextField = "stud_ID";
        ddlstudID.DataValueField = "stud_ID";
        ddlstudID.DataBind();
        ddlstudID.Items.Insert(0, new ListItem("Please Select", "0"));
        
    }
    private void CheckSession()
    {
        if (Session["SecurityLevel"] == null)
        {
            Response.Redirect("~/frmLogin.aspx");
        }

    }
    protected void Page_Load(object sender, EventArgs e)
    {
        CheckSession();

        if (!IsPostBack)
        {
            
            PopClass();
            PopStud();

        }
        else
        {
            ddlstudID.DataBind();
            ddlclassSelect.DataBind();
            
        }
    }
    protected void AddClass_Click(object sender, EventArgs e)
    {
        // Error Check so that Please Select is not there
        if (ddlstudID.SelectedValue == "0")
        {
            lblErrStudentName.Text = "Please Select a Student.";
            lblErrStudentName.Visible = true;
        }
        else
        {
            lblErrStudentName.Text = "";
            lblErrStudentName.Visible = false;
        }
        // Error Check so that Please Select is not there
        if (ddlclassSelect.SelectedValue == "0")
        {
            lblErrClassSelect.Text = "Please Select a Class.";
            lblErrClassSelect.Visible = true;
        }
        else
        {
            lblErrClassSelect.Text = "";
            lblErrClassSelect.Visible = false;
        }


        if (lblErrStudentName.Text == "" && lblErrClassSelect.Text == "")
        if (clsDataLayer.SaveSched(Server.MapPath("eAcademy_DB.mdb"),
            (Convert.ToString(ddlstudID.SelectedValue)),
            (Convert.ToString(ddlclassSelect.SelectedValue))))
        {
            txtVerifySaved.Text = "The information was saved.";
            txtVerifySaved.Visible = true;
            GridView1.DataBind(); // Refresh the bottom part.

            // Reset the index on all drop downs
            PopClass();
            PopStud();
            ddlstudID.SelectedIndex = 0;
            ddlclassSelect.SelectedIndex = 0;
        }
        else
        {
            // Make this visable to see
            txtVerifySaved.Text = "The information was NOT saved.";
            txtVerifySaved.Visible = true;
        }
    }
    protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
    {
        PopStud();
        PopClass();
        ddlstudID.SelectedIndex = 0;
        ddlclassSelect.SelectedIndex = 0;
        
    }
}