Use $select OData Query Option in ASP.NET Web API 2 service

Question

I'm trying to add OData Query Options in an existing ASP.NET Web API 2 service following this link. I only want the query options to be available in GET methods. I haven't been able to work the $select option when I try to get an item by id. How can I achieve this? This is what I have so far:

public class OrdersController : ApiController
{
    private readonly IOrderService orderService;

    public OrdersController(IOrderService orderService)
    {
        this.orderService = orderService;
    }

    [HttpGet]
    [Route("api/orders/{id}", Name = "GetOrderById")]
    [ResponseType(typeof(Order))]
    public IHttpActionResult GetOrder(ODataQueryOptions<Order> opts, [FromUri] int id)
    {
            Order order = orderService.GetOrderById(id);
            if (order == null)
            {
                return NotFound();
            }

            if (opts.SelectExpand != null)
                Request.ODataProperties().SelectExpandClause = opts.SelectExpand.SelectExpandClause;

            return Ok(order);
    }
}

When I test it (http://localhost:10240/api/orders/1?$select=OrderId) I have the following result:

{
    "OrderId": 1,
    "ExternalId": "S001",
    "TransactionType": "I",
    "BusinessAssociateId": 1,
    "DeliveryDate": "2017-06-30T21:08:50.427",
    "Priority": 5,
    "OrderType": "A",
    "Status": "F",
    "Information": "Incoming Material",
    "Device": "1",
    "BusinessAssociateName": null,
    "BusinessAssociateStreet": null,
    "BusinessAssociateCity": null,
    "OrderDetails": null
}

Answer 1

As @mumfy suggested, I missed to apply the options. The last line in GetOrder method left:

return Ok(opts.ApplyTo(Enumerable.Repeat(order, 1).AsQueryable()));