public partial class Order
    {
        internal sealed class OrderMetadata
        {
            private OrderMetadata() {}
            [Include]
            public Customer Customer { get; set; }
            public Nullable<long> CustomerId { get; set; }
            public long Id { get; set; }

            [Include]
            public EntityCollection<OrderItem> OrderItems { get; set; }

        }
    }

  //------------------------------

   public partial class OrderItem
    {
        internal sealed class OrderItemMetadata
        {
            private OrderItemMetadata() {}

            public long Id { get; set; }
            public Order Order { get; set; }
            public Nullable<long> OrderId { get; set; }
 
            [Include]
            public Product Product { get ; set; }

            public Nullable<long> ProductId { get; set; }

        }
    }

//----------------------------------------

   public partial class Product
    {
        internal sealed class ProductMetadata
        {
            private ProductMetadata() {}

            public long Id { get; set; }
            public string Description { get; set; }

            [Include]
            public Uom Uom { get; set; }

            public Nullable<long> UomId { get; set; }

        }
    }