JSON.Net Self referencing loop detected

Question

I have a mssql database for my website within 4 tables.

When I use this:

public static string GetAllEventsForJSON()
{
    using (CyberDBDataContext db = new CyberDBDataContext())
    {
        return JsonConvert.SerializeObject((from a in db.Events where a.Active select a).ToList(), new JavaScriptDateTimeConverter());
    }
}

The code results in the following error:

Newtonsoft.Json.JsonSerializationException: Self referencing loop detected for property 'CyberUser' with type 'DAL.CyberUser'. Path '[0].EventRegistrations[0].CyberUser.UserLogs[0]'.

Answer 1

I just had the same problem with Parent/Child collections and found that post which has solved my case. I Only wanted to show the List of parent collection items and didn't need any of the child data, therefore i used the following and it worked fine:

JsonConvert.SerializeObject(ResultGroups, Formatting.None,
                        new JsonSerializerSettings()
                        { 
                            ReferenceLoopHandling = ReferenceLoopHandling.Ignore
                        });

JSON.NET Error Self referencing loop detected for type

it also referes to the Json.NET codeplex page at:

http://json.codeplex.com/discussions/272371

Documentation: ReferenceLoopHandling setting

Answer 2

The fix is to ignore loop references and not to serialize them. This behaviour is specified in JsonSerializerSettings.

Single JsonConvert with an overload:

JsonConvert.SerializeObject((from a in db.Events where a.Active select a).ToList(), Formatting.Indented,
    new JsonSerializerSettings() {
        ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
    }
);

If you'd like to make this the default behaviour, add a Global Setting with code in Application_Start() in Global.asax.cs:

JsonConvert.DefaultSettings = () => new JsonSerializerSettings {
     Formatting = Newtonsoft.Json.Formatting.Indented,
     ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
};

Reference: https://github.com/JamesNK/Newtonsoft.Json/issues/78

Answer 3

If using ASP.NET Core MVC, add this to the ConfigureServices method of your startup.cs file:

services.AddMvc()
    .AddJsonOptions(
        options => options.SerializerSettings.ReferenceLoopHandling =            
        Newtonsoft.Json.ReferenceLoopHandling.Ignore
    );

Answer 4

This may help you.

public MyContext() : base("name=MyContext") 
{ 
    Database.SetInitializer(new MyContextDataInitializer()); 
    this.Configuration.LazyLoadingEnabled = false; 
    this.Configuration.ProxyCreationEnabled = false; 
} 

http://code.msdn.microsoft.com/Loop-Reference-handling-in-caaffaf7

Answer 5

You must set Preserving Object References:

var jsonSerializerSettings = new JsonSerializerSettings
{
    PreserveReferencesHandling = PreserveReferencesHandling.Objects
};

Then call your query var q = (from a in db.Events where a.Active select a).ToList(); like

string jsonStr = Newtonsoft.Json.JsonConvert.SerializeObject(q, jsonSerializerSettings);

See: https://www.newtonsoft.com/json/help/html/PreserveObjectReferences.htm

Answer 6

I am using Dot.Net Core 3.1 and did an search for

"Newtonsoft.Json.JsonSerializationException: Self referencing loop detected for property "

I am adding this to this question, as it will be an easy reference. You should use the following in the Startup.cs file:

 services.AddControllers()
                .AddNewtonsoftJson(options =>
                {
                    // Use the default property (Pascal) casing
                    options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
                    options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
                });

Answer 7

for asp.net core 3.1.3 this worked for me

services.AddControllers().AddNewtonsoftJson(opt=>{
            opt.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
        });

Answer 8

Add "[JsonIgnore]" to your model class

{
  public Customer()
  {
    Orders = new Collection<Order>();
  }

public int Id { get; set; }
public string Name { get; set; }
public string Surname { get; set; }

[JsonIgnore]
public ICollection<Order> Orders { get; set; }
}

Answer 9

The JsonSerializer instance can be configured to ignore reference loops. Like in the following, this function allows to save a file with the content of the json serialized object:

    public static void SaveJson<T>(this T obj, string FileName)
    {
   
       JsonSerializer serializer = new JsonSerializer();
        serializer.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
        using (StreamWriter sw = new StreamWriter(FileName))
        {
            using (JsonWriter writer = new JsonTextWriter(sw))
            {
                writer.Formatting = Formatting.Indented;
                serializer.Serialize(writer, obj);
            }
        }
    }

Answer 10

If you are like me and were previously calling SerializeObject with a converter, you will need to remove the converter parameter and add it to your config... Like so:

var isoConvert = new IsoDateTimeConverter();
isoConvert.DateTimeFormat = _dateFormat;
List<JsonConverter> converters = new List<JsonConverter>();
converters.Add(isoConvert);
JsonSerializerSettings settings = new JsonSerializerSettings()
{
    PreserveReferencesHandling = PreserveReferencesHandling.Objects,
    ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
    Converters = converters
};

// Old Code:
//response.Write(JsonConvert.SerializeObject(Data, isoConvert);
response.Write(JsonConvert.SerializeObject(Data, settings));

Answer 11

JsonConvert.SerializeObject(ObjectName, new JsonSerializerSettings(){ PreserveReferencesHandling = PreserveReferencesHandling.Objects, Formatting = Formatting.Indented });

Answer 12

Sometimes you have loops becouse your type class have references to other classes and that classes have references to your type class, thus you have to select the parameters that you need exactly in the json string, like this code.

List<ROficina> oficinas = new List<ROficina>();
oficinas = /*list content*/;
var x = JsonConvert.SerializeObject(oficinas.Select(o => new
            {
                o.IdOficina,
                o.Nombre
            }));

Answer 13

Make sure you aren't missing any await keywords

You can get this error if you make a silly mistake like forgetting to await an asynchronous method.

    public async Task<JsonResult> GetTaxTable([FromServices] TaxService taxService)
    {
        var taxTable = /* await */ taxService.GetTaxTable();
        return new JsonResult(taxTable);
    }

Given that GetTaxTable is an async function, if you forget to await it you'll inadvertently end up passing a Task to the JsonResult constructor - and a Task isn't serializable so while it may at first look like everything just blew up on you - the simple solution is just to add await.