Web API - Order link handler

OrderLInkHandler.cs

public class OrderLinkHandler : HttpOperationHandler<ILinkable<Order>,ILinkable<Order>>
{
  public ILinkable<Order> OnHandle(ILinkable<Order> linkedOrder) {
    if (linkedOrder.Instance.State == OrderStates.Created) {
      linkedOrder.Links.Add(OrderLinks.Approval,
        GetApprovalUri(order.ID));
    }

    //other state logic here
    return linkedOrder;
  }

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