how to check session timeout

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MVC4

i am trying following code..but its not working....is it right way to check session timeout..plz help i am new to this..

//in global.asax

protected void Session_Start(object sender, EventArgs e)
       {
           if (Context.Session != null)
           {
               if (Context.Session.IsNewSession)
               {
                   string sCookieHeader = Request.Headers["Cookie"];

                   if ((null != sCookieHeader) && (sCookieHeader.IndexOf("ASP.NET_SessionId") >= 0))
                   {

                       HttpContextBase httpContext = new HttpContextWrapper(HttpContext.Current);
                       UrlHelper urlHelper = new UrlHelper(new RequestContext(httpContext, new RouteData()));
                       string redirectUrl = urlHelper.Action("SessionExpire", "Home");

                       httpContext.RewritePath(redirectUrl);

                   }
               }
           }
       }

//web.config
<sessionstate mode="InProc" timeout="1">