How to return javascript in mvc when I click the button to jump from one page to another and cookie overtime?

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C#

ASP.NET

C#4.0

MVC

When user log in my web,I set the cookie's timeout to be 30 min,after timeout,when user want to go to page B from page A,I will check the cookie time out and return the javascript to the brower,what's wrong with my codes?It seems that I return the content because all the codes below will display in the browser but not execute(and I have to refresh the url and is OK).

Method 1:not work

public override void OnAuthorization(AuthorizationContext filterContext)
 {
    var url = string.Format("{0}?ReturnUrl={1}",
              FormsAuthentication.LoginUrl,
              filterContext.HttpContext.Request.RawUrl);
    if (SessionHelper.Get("UserName") == null)
    filterContext.HttpContext.Response.Write(
     "<script>alert('Login overtime!Loggin again please!');
     window.location.href='"+url +"';</script>");
 }

Method 2:not work

public override void OnAuthorization(AuthorizationContext filterContext)
  {
     var url = string.Format("{0}?ReturnUrl={1}",
               FormsAuthentication.LoginUrl,
               filterContext.HttpContext.Request.RawUrl);
     if (SessionHelper.Get("UserName") == null)
      filterContext.Result = new ContentResult
       {
        ContentType = "text/html",
        Content = "<script>alert('Login overtime!Loggin again please!');
       window.location.href='" + url + "';<script>"
       };
    }