ASP.NET MVC 4 Custom Authorize Attribute with Permission Codes (without roles)

I could do this with a custom attribute as follows.

[AuthorizeUser(AccessLevel = "Create")]
public ActionResult CreateNewInvoice()
{
    //...
    return View();
}

Custom Attribute class as follows.

public class AuthorizeUserAttribute : AuthorizeAttribute
{
    // Custom property
    public string AccessLevel { get; set; }

    protected override bool AuthorizeCore(HttpContextBase httpContext)
    {
        var isAuthorized = base.AuthorizeCore(httpContext);
        if (!isAuthorized)
        {                
            return false;
        }

        string privilegeLevels = string.Join("", GetUserRights(httpContext.User.Identity.Name.ToString())); // Call another method to get rights of the user from DB

        return privilegeLevels.Contains(this.AccessLevel);           
    }
}

You can redirect an unauthorised user in your custom AuthorisationAttribute by overriding the HandleUnauthorizedRequest method:

protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
{
    filterContext.Result = new RedirectToRouteResult(
                new RouteValueDictionary(
                    new
                        { 
                            controller = "Error", 
                            action = "Unauthorised" 
                        })
                );
}