JSON.NET Error Self referencing loop detected for type

Question

I tried to serialize POCO class that was automatically generated from Entity Data Model .edmx and when I used

JsonConvert.SerializeObject 

I got the following error:

Error Self referencing loop detected for type System.data.entity occurs.

How do I solve this problem?

Answer 1

Use JsonSerializerSettings

• ReferenceLoopHandling.Error (default) will error if a reference loop is encountered. This is why you get an exception.
• ReferenceLoopHandling.Serialize is useful if objects are nested but not indefinitely.
• ReferenceLoopHandling.Ignore will not serialize an object if it is a child object of itself.

Example:

JsonConvert.SerializeObject(YourPOCOHere, Formatting.Indented, 
new JsonSerializerSettings 
{ 
        ReferenceLoopHandling = ReferenceLoopHandling.Serialize
});

Should you have to serialize an object that is nested indefinitely you can use PreserveObjectReferences to avoid a StackOverflowException.

Example:

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

Pick what makes sense for the object you are serializing.

Reference http://james.newtonking.com/json/help/

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

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

The simplest way to do this is to install Json.NET from nuget and add the [JsonIgnore] attribute to the virtual property in the class, for example:

    public string Name { get; set; }
    public string Description { get; set; }
    public Nullable<int> Project_ID { get; set; }

    [JsonIgnore]
    public virtual Project Project { get; set; }

Although these days, I create a model with only the properties I want passed through so it's lighter, doesn't include unwanted collections, and I don't lose my changes when I rebuild the generated files...

Answer 4

In .NET Core 1.0, you can set this as a global setting in your Startup.cs file:

using System.Buffers;
using Microsoft.AspNetCore.Mvc.Formatters;
using Newtonsoft.Json;

// beginning of Startup class

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc(options =>
        {
            options.OutputFormatters.Clear();
            options.OutputFormatters.Add(new JsonOutputFormatter(new JsonSerializerSettings(){
                ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
            }, ArrayPool<char>.Shared));
        });
    }

Answer 5

If you're using .NET Core 2.x, update your ConfigureServices section in Startup.cs

https://learn.microsoft.com/en-us/ef/core/querying/related-data/serialization

    public void ConfigureServices(IServiceCollection services)
    {
    ...

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

    ...
    }

If you're using .NET Core 3.x - 5.0, without MVC, it would be:

# startup.cs
services.AddControllers()
  .AddNewtonsoftJson(options =>
      options.SerializerSettings.ReferenceLoopHandling =
        Newtonsoft.Json.ReferenceLoopHandling.Ignore
   );

For .NET 6.0, the only difference is it now goes in Program.cs.

# program.cs
services.AddControllers()
   .AddNewtonsoftJson(options =>
      options.SerializerSettings.ReferenceLoopHandling = 
        Newtonsoft.Json.ReferenceLoopHandling.Ignore);

This reference loop handling is almost mandatory if you're using Entity Framework and database-first design pattern.

Answer 6

We can add these two lines into DbContext class constructor to disable Self referencing loop, like

public TestContext()
        : base("name=TestContext")
{
    this.Configuration.LazyLoadingEnabled = false;
    this.Configuration.ProxyCreationEnabled = false;
}

Answer 7

To serialize usin NEWTONSOFTJSON when you have loop issue, in my case I did not need modify global.asax or either apiconfig. I just use JsonSerializesSettings ignoring Looping handling.

JsonSerializerSettings jss = new JsonSerializerSettings();
jss.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
var lst = db.shCards.Where(m => m.CardID == id).ToList();
string json = JsonConvert.SerializeObject(lst, jss);

Answer 8

You can apply an attribute to the property too. The [JsonProperty( ReferenceLoopHandling = ... )] attribute is well suited to this.

For example:

/// <summary>
/// Represents the exception information of an event
/// </summary>
public class ExceptionInfo
{
    // ...code omitted for brevity...

    /// <summary>
    /// An inner (nested) error.
    /// </summary>
    [JsonProperty( ReferenceLoopHandling = ReferenceLoopHandling.Ignore, IsReference = true )]
    public ExceptionInfo Inner { get; set; }

    // ...code omitted for brevity...    
}

Hope that helps, Jaans

Answer 9

To ignore loop references and not to serialize them globally in MVC 6 use the following in startup.cs:

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc().Configure<MvcOptions>(options =>
        {
            options.OutputFormatters.RemoveTypesOf<JsonOutputFormatter>();
            var jsonOutputFormatter = new JsonOutputFormatter();
            jsonOutputFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
            options.OutputFormatters.Insert(0, jsonOutputFormatter);
        });
    }

Answer 10

Just update services.AddControllers() in Startup.cs file

services.AddControllers()
  .AddNewtonsoftJson(options =>
      options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
   );

Answer 11

C# code:

var jsonSerializerSettings = new JsonSerializerSettings
{
    ReferenceLoopHandling = ReferenceLoopHandling.Serialize,
    PreserveReferencesHandling = PreserveReferencesHandling.Objects,
};

var jsonString = JsonConvert.SerializeObject(object2Serialize, jsonSerializerSettings);

var filePath = @"E:\json.json";

File.WriteAllText(filePath, jsonString);

Answer 12

Use this in WebApiConfig.cs class :

var json = config.Formatters.JsonFormatter;
json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
config.Formatters.Remove(config.Formatters.XmlFormatter);

Answer 13

For me I had to go a different route. Instead of trying to fix the JSON.Net serializer I had to go after the Lazy Loading on my datacontext.

I just added this to my base repository:

context.Configuration.ProxyCreationEnabled = false;

The "context" object is a constructor parameter I use in my base repository because I use dependency injection. You could change the ProxyCreationEnabled property anywhere you instantiate your datacontext instead.

http://techie-tid-bits.blogspot.com/2015/09/jsonnet-serializer-and-error-self.html

Answer 14

I had this exception and my working solution is Easy and Simple,

Ignore the Referenced property by adding the JsonIgnore attribute to it:

[JsonIgnore]
public MyClass currentClass { get; set; }

Reset the property when you Deserialize it:

Source = JsonConvert.DeserializeObject<MyObject>(JsonTxt);
foreach (var item in Source)
        {
            Source.MyClass = item;
        }

using Newtonsoft.Json;

Answer 15

Team:

This works with ASP.NET Core; The challenge to the above is how you 'set the setting to ignore'. Depending on how you setup your application it can be quite challenging. Here is what worked for me.

This can be placed in your public void ConfigureServices(IServiceCollection services) section.

services.AddMvc().AddJsonOptions(opt => 
        { 
      opt.SerializerSettings.ReferenceLoopHandling =
      Newtonsoft.Json.ReferenceLoopHandling.Ignore;
        });

Answer 16

People have already talked about [JsonIgnore] being added to the virtual property in the class, for example:

[JsonIgnore]
public virtual Project Project { get; set; }

I will also share another option, [JsonProperty(NullValueHandling = NullValueHandling.Ignore)] which omits the property from serialization only if it is null:

[JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
public virtual Project Project { get; set; }

Answer 17

In .Net 5.x, update your ConfigureServices method in startup.cs with the below code

public void ConfigureServices(IServiceCollection services)
{
    ----------------
    ----------------
    services.AddMvc().AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.Preserve;
    });
    ------------------
}

By default, serialization (System.Text.Json.Serialization) does not support objects with cycles and does not preserve duplicate references. Use Preserve to enable unique object reference preservation on serialization and metadata consumption to read preserved references on deserialization. MSDN Link

Answer 18

My Problem Solved With Custom Config JsonSerializerSettings:

services.AddMvc(
  // ...
               ).AddJsonOptions(opt =>
                 {
                opt.SerializerSettings.ReferenceLoopHandling =
                    Newtonsoft.Json.ReferenceLoopHandling.Serialize;
                opt.SerializerSettings.PreserveReferencesHandling =
                    Newtonsoft.Json.PreserveReferencesHandling.Objects;
                 });

Answer 19

For .NET Core 3.0, update the Startup.cs class as shown below.

public void ConfigureServices(IServiceCollection services)
{
...

services.AddControllers()
    .AddNewtonsoftJson(
        options => options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
    );

...
}

See: https://devblogs.microsoft.com/aspnet/asp-net-core-updates-in-net-core-3-0-preview-5/

Answer 20

Please also make sure to use await and async in you method. You can get this error if your object are not serialized properly.

Answer 21

I've inherited a database application that serves up the data model to the web page. Serialization by default will attempt to traverse the entire model tree and most of the answers here are a good start on how to prevent that.

One option that has not been explored is using interfaces to help. I'll steal from an earlier example:

public partial class CompanyUser
{
    public int Id { get; set; }
    public int CompanyId { get; set; }
    public int UserId { get; set; }

    public virtual Company Company { get; set; }

    public virtual User User { get; set; }
}

public interface IgnoreUser
{
    [JsonIgnore]
    User User { get; set; }
}

public interface IgnoreCompany
{
    [JsonIgnore]
    User User { get; set; }
}

public partial class CompanyUser : IgnoreUser, IgnoreCompany
{
}

No Json settings get harmed in the above solution. Setting the LazyLoadingEnabled and or the ProxyCreationEnabled to false impacts all your back end coding and prevents some of the true benefits of an ORM tool. Depending on your application the LazyLoading/ProxyCreation settings can prevent the navigation properties loading without manually loading them.

Here is a much, much better solution to prevent navigation properties from serializing and it uses standard json functionality: How can I do JSON serializer ignore navigation properties?

Answer 22

Simply place Configuration.ProxyCreationEnabled = false; inside the context file; this will solve the problem.

public demEntities()
    : base("name=demEntities")
{
    Configuration.ProxyCreationEnabled = false;
}

Answer 23

I was facing the same problem and I tried using JsonSetting to ignore the self-referencing error its kinda work until I got a class which self-referencing very deeply and my dot-net process hangs on Json writing value.

My Problem

    public partial class Company : BaseModel
{
    public Company()
    {
        CompanyUsers = new HashSet<CompanyUser>();
    }

    public string Name { get; set; }

    public virtual ICollection<CompanyUser> CompanyUsers { get; set; }
}

public partial class CompanyUser
{
    public int Id { get; set; }
    public int CompanyId { get; set; }
    public int UserId { get; set; }

    public virtual Company Company { get; set; }

    public virtual User User { get; set; }
}

public partial class User : BaseModel
{
    public User()
    {
        CompanyUsers = new HashSet<CompanyUser>();
    }

    public string DisplayName { get; set; }
    public virtual ICollection<CompanyUser> CompanyUsers { get; set; }

}

You can see the problem in User class it's referencing to CompanyUser class which is a self-referencing.

Now, I'm calling the GetAll Method which includes all the relational properties.

cs.GetAll("CompanyUsers", "CompanyUsers.User");

On this stage my DotNetCore process hangs on Executing JsonResult, writing value ... and never come. In my Startup.cs, I've already set the JsonOption. For some reason EFCore is including nested property which I'm not asking Ef to give.

    options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;

expected behavior should be this

Hey EfCore can you please include "CompanyUsers" data as well in my Company class so that i can easily access the data.

then

Hey EfCore can you also please include the "CompanyUsers.User" data as well so that i can easily access the data like this Company.CompanyUsers.First().User.DisplayName

at this stage i should only get this "Company.CompanyUsers.First().User.DisplayName" and it should not give me Company.CompanyUsers.First().User.CompanyUsers which causing the self-referencing issue; Technically it shouldn't give me User.CompanyUsers as CompanyUsers is a navigational property. But, EfCore get very excited and giving me User.CompanyUsers.

So, I decided to write an extension method for property to be excluded from the object (it's actually not excluding it's just setting the property to null). Not only that it will also work on array properties as well. below is the code I'm also going to export the nuget package for other users (not sure if this even helps someone). Reason is simple because I'm too lazy to write .Select(n => new { n.p1, n.p2}); I just don't want to write select statement to exclude only 1 property!

This is not the best code (I'll update at some stage) as I have written in a hurry and though this might help someone who wants to exclude (set null) in the object with arrays also.

    public static class PropertyExtensions
{
    public static void Exclude<T>(this T obj, Expression<Func<T, object>> expression)
    {
        var visitor = new PropertyVisitor<T>();
        visitor.Visit(expression.Body);
        visitor.Path.Reverse();
        List<MemberInfo> paths = visitor.Path;
        Action<List<MemberInfo>, object> act = null;

        int recursiveLevel = 0;
        act = (List<MemberInfo> vPath, object vObj) =>
        {

            // set last propert to null thats what we want to avoid the self-referencing error.
            if (recursiveLevel == vPath.Count - 1)
            {
                if (vObj == null) throw new ArgumentNullException("Object cannot be null");

                vObj.GetType().GetMethod($"set_{vPath.ElementAt(recursiveLevel).Name}").Invoke(vObj, new object[] { null });
                return;
            }

            var pi = vObj.GetType().GetProperty(vPath.ElementAt(recursiveLevel).Name);
            if (pi == null) return;
            var pv = pi.GetValue(vObj, null);
            if (pi.PropertyType.IsArray || pi.PropertyType.Name.Contains("HashSet`1") || pi.PropertyType.Name.Contains("ICollection`1"))
            {
                var ele = (IEnumerator)pv.GetType().GetMethod("GetEnumerator").Invoke(pv, null);

                while (ele.MoveNext())
                {
                    recursiveLevel++;
                    var arrItem = ele.Current;

                    act(vPath, arrItem);

                    recursiveLevel--;
                }

                if (recursiveLevel != 0) recursiveLevel--;
                return;
            }
            else
            {
                recursiveLevel++;
                act(vPath, pv);
            }

            if (recursiveLevel != 0) recursiveLevel--;

        };

        // check if the root level propert is array
        if (obj.GetType().IsArray)
        {
            var ele = (IEnumerator)obj.GetType().GetMethod("GetEnumerator").Invoke(obj, null);
            while (ele.MoveNext())
            {
                recursiveLevel = 0;
                var arrItem = ele.Current;

                act(paths, arrItem);
            }
        }
        else
        {
            recursiveLevel = 0;
            act(paths, obj);
        }

    }

    public static T Explode<T>(this T[] obj)
    {
        return obj.FirstOrDefault();
    }

    public static T Explode<T>(this ICollection<T> obj)
    {
        return obj.FirstOrDefault();
    }
}

above extension class will give you the ability to set the property to null to avoid the self-referencing loop even arrays.

Expression Builder

    internal class PropertyVisitor<T> : ExpressionVisitor
{
    public readonly List<MemberInfo> Path = new List<MemberInfo>();

    public Expression Modify(Expression expression)
    {
        return Visit(expression);
    }


    protected override Expression VisitMember(MemberExpression node)
    {
        if (!(node.Member is PropertyInfo))
        {
            throw new ArgumentException("The path can only contain properties", nameof(node));
        }

        Path.Add(node.Member);
        return  base.VisitMember(node);
    }
}

Usages:

Model Classes

    public class Person
{
    public string Name { get; set; }
    public Address AddressDetail { get; set; }
}

public class Address
{
    public string Street { get; set; }
    public Country CountryDetail { get; set; }
    public Country[] CountryDetail2 { get; set; }
}

public class Country
{
    public string CountryName { get; set; }
    public Person[] CountryDetail { get; set; }
}

Dummy Data

           var p = new Person
        {
            Name = "Adeel Rizvi",
            AddressDetail = new Address
            {
                Street = "Sydney",
                CountryDetail = new Country
                {
                    CountryName = "AU"
                }
            }
        };

        var p1 = new Person
        {
            Name = "Adeel Rizvi",
            AddressDetail = new Address
            {
                Street = "Sydney",
                CountryDetail2 = new Country[]
                {
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A1" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A2" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A3" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A4" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A5" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A6" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A7" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A8" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A9" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A1" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A2" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A3" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A4" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A5" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A6" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A7" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A8" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
                    new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A9" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },

                }
            }
        };

Cases:

Case 1: Exclude only property without any array

p.Exclude(n => n.AddressDetail.CountryDetail.CountryName);

Case 2: Exclude property with 1 array

p1.Exclude(n => n.AddressDetail.CountryDetail2.Explode().CountryName);

Case 3: Exclude property with 2 nested array

p1.Exclude(n => n.AddressDetail.CountryDetail2.Explode().CountryDetail.Explode().Name);

Case 4: EF GetAll Query With Includes

var query = cs.GetAll("CompanyUsers", "CompanyUsers.User").ToArray();
query.Exclude(n => n.Explode().CompanyUsers.Explode().User.CompanyUsers);
return query;

You have notice that Explode() method its also a extension method just for our expression builder to get the property from array property. Whenever there is a array property use the .Explode().YourPropertyToExclude or .Explode().Property1.MyArrayProperty.Explode().MyStupidProperty. Above code helps me to avoid the self-referencing so deep as deep i want. Now i can use GetAll and exclude the property which i don;t want!

Thank you for reading this big post!

Answer 24

Very similar to others on here, Solved by using the Serializer settings. However mine originated since I was using the FromObject side of things as I needed a JObject to work with.

This means just need to create the default serializer and apply settings to that. Simple fix becomes this

 var deserializerSettings = new JsonSerializerSettings()
        {
            ReferenceLoopHandling = ReferenceLoopHandling.Serialize,
            PreserveReferencesHandling = PreserveReferencesHandling.Objects,
        };

        var serializer = JsonSerializer.CreateDefault(deserializerSettings);
            
        JObject jsonObject = (JObject)JToken.FromObject(mySelfRefernceObject, serializer);

Answer 25

Had this issue coming from one of third party nuget package. Didn't have the option to change configurations or serialization. Installing Newtonsoft.Json package in my consumer project sorted the issue.

<PackageReference Include="Newtonsoft.Json" Version="13.0.2" />

Answer 26

For not looping this worked for me-
ReferenceLoopHandling = ReferenceLoopHandling.Ignore,

I've solved it all here - Entity Framework children serialization with .Net Core 2 WebAPI https://gist.github.com/Kaidanov/f9ad0d79238494432f32b8407942c606

Will appreciate any remarks. maybe someone can use it sometime.

Answer 27

I liked the solution that does it from Application_Start() as in the answer here

Apparently I could not access the json objects in JavaScript using the configuration within my function as in DalSoft's answer as the object returned had "\n \r" all over the (key, val) of the object.

Anyway whatever works is great (because different approaches work in different scenario based on the comments and questions asked) though a standard way of doing it would be preferable with some good documentation supporting the approach.