// POST odata/Airports
        public IHttpActionResult Post(Airport airport)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            TripPinSvcDataSource.Instance.Airports.Add(airport);
            return Created(airport);
        }
        // PUT odata/Airports('key')
        public IHttpActionResult Put([FromODataUri] string key, Airport airport)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            if (key != airport.IcaoCode)
            {
                return BadRequest("The IcalCode of Airline does not match the key");
            }

            var oldAirport = TripPinSvcDataSource.Instance.Airports.SingleOrDefault(item => item.IcaoCode == key);
            if (oldAirport == null)
            {
                return NotFound();
            }

            TripPinSvcDataSource.Instance.Airports.Remove(oldAirport);
            TripPinSvcDataSource.Instance.Airports.Add(airport);

            return Updated(airport);
        }