浏览器关闭后，会话变为空

我使用以下代码在页面中检索登录用户标识

// login method of account model
public ActionResult Login(LoginModel model)
{
    Session["username"]=model.Username;
    //redirect to login controler
}

和登录控制器

public ActionResult LoginLayout()
{
    if(IsAdmin(Session["username"]))
        return View();
    else
        return OtherView();
}

一切都很好，直到我关闭浏览器然后重新打开它，我总是被重定向到OtherView()，即使我仍然是登录用户。

更新

    [HttpPost]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public ActionResult Login(LoginModel model, string returnUrl)
    {
        if (ModelState.IsValid && WebSecurity.Login(model.UserName, model.Password, persistCookie: model.RememberMe))
        {                
            Session["username"] = model.UserName;
            return RedirectToLocal(returnUrl);
        }
        // If we got this far, something failed, redisplay form
        ModelState.AddModelError("", "The user name or password provided is incorrect.");
        return View(model);
    }