Asp.net Mvc - Handle Application Security Using ActionFilterAttribute And/or SiteMap Authorization?

i created the following ActionFilterAttribute to check if a user is granted access to a page. I also created two custom Exceptions to handle different scenarios: NotLoggedInException and InsufficientPrivilegeException.

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Where do I catch the exceptions to for instance redirect users if not authorized?Should I perhaps use the SiteMap authorization somewhere else instead of using the ActionFilterAttribute and throwing Exceptions..?

note: as you can see I'm using a custom class for BLL.Page. This is a ORM page which has Role based security stored in the database. SiteMap is also populated based on this data