(WebApi) Can't serialize collection of objects to Json - arrays

Question

In my WebApi controller I have a few methods that return objects retrieved from a database which are serialized to Json. Everything works fine if a method serializes and returns only a single object, it fails when it tries to serialize a collection of objects.
This is my model class:
[Table("Athlete")]
public partial class Athlete
{
public Athlete()
{
Event = new HashSet<Event>();
User = new HashSet<User>();
}
[Required]
[StringLength(32)]
[DisplayName("First name")]
public string FirstName { get; set; }
[Required]
[StringLength(32)]
[DisplayName("Last name")]
public string LastName { get; set; }
[StringLength(32)]
[DisplayName("Sport")]
public string Sport { get; set; }
[Key]
[Column(TypeName = "numeric")]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public decimal Athlete_ID { get; set; }
[DataMember]
[Column(TypeName = "numeric")]
public decimal? Team_Team_ID { get; set; }
[NotMapped]
[DisplayName("Team")]
public string TeamName { get; set; }
[JsonIgnore]
public virtual Team Team { get; set; }
[JsonIgnore]
public virtual ICollection<Event> Event { get; set; }
[JsonIgnore]
public virtual ICollection<User> User { get; set; }
}
This works fine:
[HttpGet]
public IHttpActionResult GetById(int id)
{
var athlete = _db.Athlete
.Where(a => a.Athlete_ID == id)
.FirstOrDefault();
if (athlete != null)
{
return Json<Athlete>(athlete);
}
return NotFound();
}
The following method causes a serialization error (System.InvalidOperationException)
(The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.)
The inner exception's message is "Self referencing loop detected for property 'ApplicationInstance' with type 'ASP.global_asax'. Path 'Request.Properties.MS_HttpContext.ApplicationInstance.Context'."
[HttpGet]
public IHttpActionResult GetAllAthletes()
{
var athletes = _db.Athlete.ToArray();
if (athletes != null)
{
return Ok(Json<IEnumerable<Athlete>>(athletes));
}
return NotFound();
}
I've already tried to change the serialization settings in WebApiConfig.cs like in this question but nothing has worked so far.
Any help would be appreciated.

Answer 1

I've managed to find a way to work-around this in a semi-elegant manner. I'm not completely happy with this but a man's gotta do what a man's gotta do.
In case anyone needs this in the future:
Create a class that implements the IHttpActionResult interface:
public class MyJsonResult : IHttpActionResult
{
object _value;
HttpRequestMessage _request;
public MyJsonResult(object value, HttpRequestMessage request)
{
_value = value;
_request = request;
}
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
var response = new HttpResponseMessage()
{
Content = new StringContent(JsonConvert.SerializeObject(_value), Encoding.UTF8, "application/json"),
RequestMessage = _request,
StatusCode = HttpStatusCode.OK
};
return Task.FromResult(response);
}
}
Then use it in a following way:
[HttpGet]
public IHttpActionResult GetAllAthletes()
{
var athletes = _db.Athlete;
if (athletes != null)
{
return new MyJsonResult(athletes, Request);
}
return NotFound();
}