Authorize attribute that redirects to view if you're logged in but don't have permission

AuthorizeRedirect.cs

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class AuthorizeRedirect : AuthorizeAttribute
{
    public string RedirectUrl = "~/Error/Unauthorized";

    protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
    {
        base.HandleUnauthorizedRequest(filterContext);

        if (filterContext.RequestContext.HttpContext.User.Identity.IsAuthenticated)
        {
            filterContext.RequestContext.HttpContext.Response.Redirect(RedirectUrl);
        }
    }
}