unable to get value of the property 'eo_l': object is null or unidentified

Unhandled exception at line 6, column 31641 in http://localhost:60468/eo_web.ashx?id=b8c5bf7a-9b2d-40d1-9968-dd5a545d867c

0x800a138f - Microsoft JScript runtime error: Unable to get value of the property 'eo_l': object is null or undefined

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="EOWebTestProject._Default" %>

<%@ Register Assembly="EO.Web" Namespace="EO.Web" TagPrefix="eo" %>

<asp:Content runat="server" ID="FeaturedContent" ContentPlaceHolderID="FeaturedContent">
    <section class="featured">
        <div class="content-wrapper">
            <hgroup class="title">
                <h1><%: Title %>.</h1>
                <h2>Modify this template to jump-start your ASP.NET application.</h2>
            </hgroup>
            <p>
                To learn more about ASP.NET, visit <a href="http://asp.net" title="ASP.NET Website">http://asp.net</a>.
                The page features <mark>videos, tutorials, and samples</mark> to help you get the most from ASP.NET.
                If you have any questions about ASP.NET visit
                <a href="http://forums.asp.net/18.aspx" title="ASP.NET Forum">our forums</a>.
            </p>
        </div>
    </section>
</asp:Content>
<asp:Content runat="server" ID="BodyContent" ContentPlaceHolderID="MainContent">
   
  <p>
	EO.Web Downloader can generate dynamic download content on the fly. The 
	following sample demonstrates this feature. You can enter a line count number 
	and the downloader will dynamically generates a text file with that number of 
	lines for download.
</p>
<p>
	See remarks section for more details about how to use this feature.
</p>
    <eo:CallbackPanel ID="CallbackPanel1" runat="server" Height="150px" Width="200px" Triggers="{ControlID:Downloader1;Parameter:},{ControlID:Button1;Parameter:}">
Enter Line Count:
<asp:TextBox Runat="server" ID="TextBox1"></asp:TextBox>
<p>
	<eo:Downloader runat="server" id="Downloader1" DownloadButtonID="Button1" DirectLinkLabelID="Label1"
		DynamicContent="True" AutoHideDownloadButton="False" OnDownload="Downloader1_Download"></eo:Downloader>
	<asp:Label Runat="server" ID="Label1"></asp:Label>
</p>
<asp:Button Runat="server" ID="Button1" Text="Generate File &amp; Download"></asp:Button>
</eo:CallbackPanel>
</asp:Content>

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace EOWebTestProject
{
    public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }


        protected void Downloader1_Download(object sender, EO.Web.DownloadEventArgs e)
        {
            NameValueCollection args = new NameValueCollection();
            string key = Guid.NewGuid().ToString();
            Guid id = Guid.Empty;
            if (Guid.TryParse(key, out(id)) && id != Guid.Empty)
            {
               
                args["Key"] = key;

                e.DynamicDownload(typeof(ContentGenerator), args);
            }

        }

        //You must create a new class that derives from 
        //EO.Web.DynamicDownloadContent to dynamically
        //generate the download content
        private class ContentGenerator : EO.Web.DynamicDownloadContent
        {
            protected override void GenerateContent()
            {
                //Get the argument we passed in
                int nLineCount = 0;
                 String key = string.Empty;

                try
                {

                    nLineCount = 6;

                    key = this.Arguments["Key"]; 
                }
                catch (Exception ex)
                {
                    nLineCount = 1;
                }

                //Set the file name. You should also specify
                //contentLength (the second parameter) if you
                //know the content length in advance. The
                //browser will not be able to display progress
                //information if contentLength is not set
                SetFileName("TestDownload.txt", -1);

                //Generates the content
                for (int i = 0; i < nLineCount; i++)
                {
                    string line = string.Format("Line {0}\r\n", i + 1);

                    byte[] buffer = Encoding.ASCII.GetBytes(line);

                    Write(buffer, 0, buffer.Length);
                }
            }
        }
    }
}