Hi,
Got my head stuck with this. Say I have these simple classes:

public class Order
}
   public List<OrderItem> OrderItems {get; set;}
   // Some more properites
}
public class OrderItem
{
     //Some properties
}

Now I need a more specific Order class (with a corresponding OrderItem class) so:

public class OrderB:Order
{
  //Additional Properties
}
public OrderItemB : OrderItem
{
  //Additional properties
}

How can I have OrderB's item list be based on OrderItemB rather than OrderItem ?