File uploader image preview

<%@ WebHandler Language="C#" Class="ImageHandler" %>

using System;
using System.Web;

public class ImageHandler : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{

   public void ProcessRequest (HttpContext context) {
    //Checking whether the imagebytes session variable have anything else not doing anything

       if ((context.Session["ImageBytes"]) != null)
       {
           byte[] image = (byte[])(context.Session["ImageBytes"]);
           context.Response.ContentType = "image/JPEG";
           context.Response.BinaryWrite(image);
       }
   }

   public bool IsReusable {
       get {
           return false;
       }
   }

}

protected void btnPreview_Click(object sender, EventArgs e)

   {

       Session["ImageBytes"] = PhotoUpload.FileBytes;

       ImagePreview.ImageUrl = "~/ImageHandler.ashx";

   }