Redirecting to specified controller and action in asp.net mvc action filter

Question

I have written an action filter which detects a new session and attempts to redirect the user to a page informing them that this has happened. The only problem is I can not

Answer 1

EDIT: The original question was about how to detect session logout, and then automatically redirect to a specified controller and action. The question proved much more useful as it's current form however.

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I ended up using a combination of items to achieve this goal.

First is the session expire filter found here. Then I wanted someway to specify the controller/action combo to get a redirect URL, which I found plenty of examples of here. In the end I came up with this:

public class SessionExpireFilterAttribute : ActionFilterAttribute
{
    public String RedirectController { get; set; }
    public String RedirectAction { get; set; }

    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        HttpContext ctx = HttpContext.Current;

        if (ctx.Session != null)
        {
            if (ctx.Session.IsNewSession)
            {
                string sessionCookie = ctx.Request.Headers["Cookie"];
                if ((null != sessionCookie) && (sessionCookie.IndexOf("ASP.NET_SessionId") >= 0))
                {
                    UrlHelper helper = new UrlHelper(filterContext.RequestContext);
                    String url = helper.Action(this.RedirectAction, this.RedirectController);
                    ctx.Response.Redirect(url);
                }
            }
        }

        base.OnActionExecuting(filterContext);
    }
}