Web API - Order link service

OrderLinkService.cs

public class OrderLinkService : IOrderLinkService, ILinkService<Order> {
  public ILinkable<Order> AddLinks(Order order) {
    var linkedOrder = new Linkable<Order>();
    if (order.State == OrderStates.Created) {
      linkedOrder.Links.Add(OrderLinks.Approval, GetApprovalUri(order.ID));
    }

    //other state logic here
    return linkedOrder;
  }

  private Uri GetApprovalUri(orderid) {
    ...
  }
}