asp.net - ASP MVC Authorize all actions except a few

Question

I have a controller and I would like to require Authorization for all actions by default except a couple. So in the example below all actions should require authentication except the Index. I don't want to decorate every action with the Authorize, I just want to override the default authorization in certain circumstances probably with a custom filter such as NotAuthorize.

[Authorize]
public class HomeController : BaseController
{
    [NotAuthorize]
    public ActionResult Index()
    {
        // This one wont
        return View();
    }

    public ActionResult About()
    {
        // This action will require authorization
        return View();
    }
}

Answer 1

Ok, this is what I did. If there is a better way let me know.

public class NotAuthorizeAttribute : FilterAttribute
{
    // Does nothing, just used for decoration
}

public class BaseController : Controller
{
    protected override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // Check if this action has NotAuthorizeAttribute
        object[] attributes = filterContext.ActionDescriptor.GetCustomAttributes(true);
        if (attributes.Any(a => a is NotAuthorizeAttribute)) return;

        // Must login
        if (!filterContext.HttpContext.User.Identity.IsAuthenticated)
        {
            filterContext.Result = new HttpUnauthorizedResult();
        }
    }
}