Download Problem in ASP.Net project

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ASP.NET

web

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Remittance.Common;
using Remittance.DAL.Entities;
using Remittance.DAL.Repo;
using Remittance.DAL;

namespace Remittance.Payment
{
    public partial class download : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
           IQueryable<transaction> src=  Session["SRC"]as IQueryable<transaction>;
            string reportName = (string)Session["reportname"];
            string extension = (string)Session["extension"];
           byte[] bytes = (byte[])Session["Byte"];
            Response.Clear();
           // Response.ContentType = mimeType;
            Session["Success"] = "Success"; 
            Response.AddHeader("Content-Disposition", "attachment; filename=" + reportName + "." + extension);
            Response.Cache.SetCacheability(HttpCacheability.NoCache);
            Response.OutputStream.Write(bytes, 0, bytes.Length);
            Response.Flush();
            Response.End();
           
        }
    }
}
</transaction></transaction>

I use this for download a file in asp.net, its work in Mozilla, google chrome, IE9
but don't work in IE6,7,8?? why
please answer me if any of u know ?
Thanks for reading.

[Edited]Code is wrapped in "pre"[/Edited]