FilterBuilder question matching comma seperated string with a list

Hi guys,

my problem:

i have a checkbox property on a catalogitem. 

public class TippingProduct : BaseProductContent
    {        
        [EnumMany(typeof(TippingFrontEndCylinderHeadboardType))]        
        [Display(Order = 8,
            Name = "Headboard Type",
            GroupName = Logic.Constants.TabNames.Filters,
            Description = "Filter Headboard Type - Frontend Cylinder")]        
        public virtual string HeadboardType { get; set; }
}

the enum looks like this:

 public enum TippingFrontEndCylinderHeadboardType
    {
        Slanted,
        Straight
    }

now i want to filter on headboardtype

public static dynamic TippingProducts(TippingSearchData tippingSearchData)
        {
            IClient client = SearchClient.Instance;
            //start of the query
            var query = client.Search<TippingProduct>()
                .FilterForVisitor()
                .Filter(x => x.ShowInList.Match(true));
            //selected headboard type
            if (tippingSearchData.Headboard != null && tippingSearchData.Headboard.Any())
            {
                query = query.Filter(x => GetHeadBoardFilter(tippingSearchData.Headboard));
            }
            var res = query.GetContentResult();
            return new
            {
                items = res.Count()
           };
        }

private static FilterBuilder<TippingProduct> GetHeadBoardFilter(List<TippingFrontEndCylinderHeadboardType> headboards)
        {
            var filter = SearchClient.Instance.BuildFilter<TippingProduct>();
           // return headboards.Aggregate(filter, (current, headboard) => current.Or(x => x.HeadboardType.Match(headboard.ToString())));
            foreach (var headboard in headboards)
            {
                filter = filter.Or(tp => tp.HeadboardType.Split(',').Match(headboard.ToString()));
            }
            return filter;
        }

So the property HeadBoardType of my TippingProduct saves the data as comma seperated string. 

When searching using epifind i sent a List<TippingFrontEndCylinderHeavyDuty> headboards and want a filter on all my TippingProduct pages where the HeadBoardType property contains one of the items from the list. 

You can see in my filter builder i had a aggregate uncommented. So that works good if each TippingProduct only has 1 checkbox selected, because then its not a comma seperated string. But once 1 tipping product has 2 checkboxes selected then that one is not found. Which is logical because it will not match. But my second approach trying to split and then check doesnt work either. So i must be missing something trivial here.