Session data lost before ticket timeout

问题

I try to set a rather long session time of 60 minutes on my web site by setting in web.config the authentication / forms / timeout value, and also by setting in code behind of the login page FormsAuthenticationTicket.expiration. However, already in 20 minutes, way too early, data in my Session variable got lost. How does this work and how do I fix it?

Web.config:

<authentication mode="Forms">
  <forms name="MYWEBAPP.ASPXAUTH" 
    loginUrl="~/Login.aspx" 
    protection="All" 
    timeout="60"                   /* <<------ */         
    slidingExpiration="true" 
    path="/"/>
</authentication>

login.aspx.cs:

            // Create a new ticket used for authentication
            FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(
                1,                                      // Ticket version
                LoggedInUser.LoginNm.ToString(),        // Username associated with ticket
                DateTime.Now,                           // Date/time issued
                DateTime.Now.AddMinutes(60), // <<---   // Date/time to expire, minutes, use same value as in web.config or result is unclear
                false,                                  // "true" for a persistent user cookie
                LoggedInUser.UserID.ToString(),         // User-data, in this case user object
                FormsAuthentication.FormsCookiePath);   // Path cookie valid for

            // Encrypt the ticket and store in a cookie
            string CookieName = FormsAuthentication.FormsCookieName;
            string CookieValue = FormsAuthentication.Encrypt(ticket);
            cookie = new HttpCookie(CookieName, CookieValue);

            // Set the cookie's expiration time to the tickets expiration time, plus a little to be sure.
            // NB: the cookie is created and updated with "sliding" reset automatically
            //  if the SetAuth...()  coockie call was used
            // NB: Persistent is false, so this is a Session cookie without expiration 
            //     that is deleted when the browser closes.
            //if (ticket.IsPersistent)
            {
                cookie.Expires = ticket.Expiration.AddMinutes(5);
            }

Check if the session is still alive in a form.aspx.cs:

protected void Page_PreInit(object sender, EventArgs e)
{
    // Load settings from session variabele
    MySession = Session["MySession"] as ClSession;
    // return to loginpage indien sessionvar = null
    if (MySession == null)
        Response.Redirect("~/SessionExpired.html"); // <<---after only 20 minutes!!??
    return;
}

来源：https://stackoverflow.com/questions/38851190/session-data-lost-before-ticket-timeout