Custom Filter not working in ASP.NET Dynamic Data

Question

I have the following metadata property on a Region:

        [FilterUIHint("ActivationCampaignFilter")]
        [DisplayName("C")]
        public object Campaigns { get; set; }

The DisplayName attribute is effective at changing the visible name of Campaigns to just "C", but the FilterUIHint attribute is simple ignored and a standard FK filter used. I have recently upgraded the application from .NET 3.5 to .NET 4. Should I rather maybe just create a new application and copy all my work over?