problem with create session after old session is timed out and get authenticaton: system.invalidoperationexception exception

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C#

ASP.NET

C#4.0

jQuery

i have a snippet that a session has numeric content nd it incrise to 3 but when it receive to 3 it send to client.this session must time out in 1 minuet but until the session is not time out the program work correctly but when the session is expired and new session want create i get system.invalidoperationexception . i check session if its expierd i creat a new but when i want create new session i get system.invalidoperationexception if i select adress bar and reload page new session create but when i use window.location.reload() in client side for refresh my problem dont solve.i use history.go(0) and other method but dont work.whats the problem????
its my code :

string ip = HttpContext.Current.Request.UserHostAddress;


HttpContext failuser = HttpContext.Current;
failuser.Session.Timeout =1;
if (failuser != null)
{
    if (failuser.Session[ip] != null)
        failuser.Session[ip] = (int)failuser.Session[ip] + 1;
    else
        failuser.Session[ip] = 1;

    //
    retval = failuser.Session[ip].ToString();
    if ((int)failuser.Session[ip] > 2)
    {

        retval = "!";

    }