How to get filter to redirect to another action?

RedirectToAction is protected, and we can use it only inside actions. But if I want to redirect in a filter?

public class IsGuestAttribute: ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (!Ctx.User.IsGuest) 
            filterContext.Result = (filterContext.Controller as Controller)
                .RedirectToAction("Index", "Home");
    }
}