application_acquirerequeststate event asp.net to prevent session hijacking

protected void Application_BeginRequest(object sender, EventArgs e)
        {
            //Check If it is a new session or not , if not then do the further checks
            if (Request.Cookies["ASP.NET_SessionId"] != null && Request.Cookies["ASP.NET_SessionId"].Value != null)
            {
                string newSessionID = Request.Cookies["ASP.NET_SessionID"].Value;
                //Check the valid length of your Generated Session ID
                if (newSessionID.Length <= 24)
                {
                    //Log the attack details here
                    Response.Cookies["TriedTohack"].Value = "True";
                    throw new HttpException("Invalid Request");
                }

                //Genrate Hash key for this User,Browser and machine and match with the Entered NewSessionID
                if (GenerateHashKey() != newSessionID.Substring(24))
                {
                    //Log the attack details here
                    Response.Cookies["TriedTohack"].Value = "True";
                    throw new HttpException("Invalid Request");
                }

                //Use the default one so application will work as usual//ASP.NET_SessionId
                Request.Cookies["ASP.NET_SessionId"].Value = Request.Cookies["ASP.NET_SessionId"].Value.Substring(0, 24);
            }

        }