(WebApi) 无法将对象集合序列化为 Json

Question

在我的 WebApi 控制器中，我有一些方法 return 从数据库中检索的对象被序列化为 Json。如果方法序列化并且 return 只有一个对象，则一切正常，但在尝试序列化对象集合时失败。

这是我的模型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; }
    }

这很好用：

[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();
}

以下方法导致序列化错误(System.InvalidOperationException) （'ObjectContent`1' 类型无法序列化内容类型 'application/json; charset=utf-8' 的响应正文。）

内部异常的消息是"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();
}

我已经尝试像在 this question 中那样更改 WebApiConfig.cs 中的序列化设置，但到目前为止没有任何效果。

如有任何帮助，我们将不胜感激。

Answer 1

我设法找到了一种半优雅的解决方法。我对此并不完全满意，但男人必须做男人必须做的事。

万一以后有人需要这个：

创建一个实现 IHttpActionResult 接口的 class：

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);
        }
    }

然后按如下方式使用：

[HttpGet]
public IHttpActionResult GetAllAthletes()
{
    var athletes = _db.Athlete;

    if (athletes != null)
    {
        return new MyJsonResult(athletes, Request);
    }

    return NotFound();
}

(WebApi) 无法将对象集合序列化为 Json

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

arrays

collections

json

asp.net-web-api2