[CollectionDataContract]
public class EntityCollection<T> : BindingList<T>, IBindingListView, IRaiseItemChangedEvents
    {       
        
        [DataMember]
        private readonly List<T> _deleted = new List<T>();
        
        public List<T> Deleted
        {
            get { return _deleted; }
        }
//Логика заполнения коллекции Deleted
//...

//Реализация интерфейсов IBindingListView, IRaiseItemChangedEvents
//...
   }