Can not start the Designer

Yordan

Hello.
I am trying to start online designer on WebForms project.

I am trying with this code:

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

namespace WebDemo
{
    public partial class Designer : System.Web.UI.Page
    {
        protected void Page_Load( object sender, EventArgs e )
        {
            WebReport1.Report.Load( @"e:\OfferPDP_horizontal.frx" );
            WebReport1.Report.Prepare();

            WebReport1.DesignReport = true; // << Seems like this row is making the crash
            
        }
    }
}

but the result is always this error page: