Json Post запрос на asp.net веб-api не работает

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Эй, ребята, у меня есть as.net приложение web api с этим контроллером:

// GET: api/Events/5
        [ResponseType(typeof(EventDto))]
        public async Task<IHttpActionResult> GetEvent(int id)
        {
            var events = await db.Events.Include(e => e.Name).Select(e =>
                new EventDto()
                {
                    Id = e.Id,
                    Name = e.Name,
                    Project = e.Project,
                    Objectives = e.Objectives,
                    City = e.City,
                    Country = e.Country,
                    EventStart = e.EventStart,
                    Departure = e.Departure,
                    Arrival = e.Arrival,
                    Registration = e.Registration,
                    NationalTransportation = e.NationalTransportation,
                    Accommodation = e.Accommodation,
                    AcNumberNights = e.AcNumberNights,
                    AcPreferHotel = e.AcPreferHotel,
                    AcPreferHotelUrl = e.AcPreferHotelUrl,
                    Flight = e.Flight,
                    FlDeparture = e.FlDeparture,
                    FlDepartPrefer = e.FlDepartPrefer,
                    FlDepartPreferUrl = e.FlDepartPreferUrl,
                    FlReturn = e.FlReturn,
                    FlRetPrefer = e.FlRetPrefer,
                    FlRetPreferUrl = e.FlRetPreferUrl,
                    Notes = e.Notes,
                    Files = e.Files,
                    Status = e.Status
                }).SingleOrDefaultAsync(e => e.Id == id);
            if (events == null)
            {
                return NotFound();
            }

            return Ok(events);
        } 

и я использую расширение postman chrome, чтобы проверить его с помощью этого json:

{
"Name": "psilva", 
"Project": "a",
"Objectives": "s",
"City": "a",
"Country": "s",
"EventStart": 2012,
"Departure": 2012,
"Arrival": 2012,
"Registration": "a",
"NationalTransportation": "a",
"Accommodation" : "a",
"AcNumberNights": 1,
"AcPreferHotel": "a",
"AcPreferHotelUrl": "a",
"Flight": "a",
"FlDeparture": 2012,
"FlDepartPrefer": "a",
"FlDepartPreferUrl": "a",
"FlReturn": 2012,
"FlRetPrefer": "a",
"FlRetPreferUrl": "a",
"Notes": "a",
"Files": "a",
"Status": "a"    
}

и я получу это от почтальона:

{
    "Message": "The request entity's media type 'text/plain' is not supported for this resource.",
    "ExceptionMessage": "No MediaTypeFormatter is available to read an object of type 'Event' from content with media type 'text/plain'.",
    "ExceptionType": "System.Net.Http.UnsupportedMediaTypeException",
    "StackTrace": "   at System.Net.Http.HttpContentExtensions.ReadAsAsync[T](HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)\r\n   at System.Net.Http.HttpContentExtensions.ReadAsAsync(HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)\r\n   at System.Web.Http.ModelBinding.FormatterParameterBinding.ReadContentAsync(HttpRequestMessage request, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)"
}

есть идеи, почему?

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