Exporting templated class

   Hello,
I'm lost in a cave with Exporting with templates...

before I have had an interface of type IDashboard that has an ID (int) and a collection of Items of type Gauge

Now I've been asked if it's possible to define another type of Gauge and continue using existing code structure..so I've defined those class

  [Export(typeof(IDashBoard<Gauge<ISnapshot>, ISnapshot>))]
    public class DashboardViewModel : DashBoardBase<Indicatore<SNAPSHOT_INDICATORE_SELECT_Result>, SNAPSHOT_INDICATORE_SELECT_Result>
    {
...
}

 public class DashBoardBase<T,Y> : Screen, IDashBoard<T, Y>
        where T : GaugeBase<Y>
        where Y : ISnapshot
    {
...
}

 public class GaugeBase<T> : INotifyPropertyChanged where T:ISnapshot
 {
...
}

 public interface ISnapshot
    {
        DateTime DT_TS { get; set; }
    }

public interface IDashBoard<T,Y> : INotifyPropertyChanged 
    where T : GaugeBase<Y>
    where Y : ISnapshot
{
    BindableCollection<T> DataItems { get; set; }

    T SelectedDataItem { get; set; }

    int IdDashBoard { get; set; }

    int IdLayout { get; }
...
}

Before I had a dashboardfactory of type

        [ImportingConstructor]
        public DashBoardFactory()
        {
            //[ImportMany(typeof(IDashboard))] IEnumerable<IDashboard listaIndicatori
            this.listaIndicatori = listaIndicatori;
        }

and it was working... now I've tried all the ways but I'm not able to set the export so that my dashboardfactory can get items

   [ImportingConstructor]
        public DashBoardFactory()
        {
            //[ImportMany(typeof(DashBoardBase<GaugeBase<ISnapshot>, ISnapshot>))] IEnumerable<DashBoardBase<GaugeBase<ISnapshot>, ISnapshot>> listaIndicatori
            this.listaIndicatori = listaIndicatori;

            var items = Cocktail.Composition.GetInstances<IDashBoard<Indicatore<ISnapshot>, ISnapshot>>();
            int count = items.Count(); //0 or it says it cannot cast to type...

        }

Any suggestion?
Thanks