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 

Answer 1

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 2

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

https://docs.microsoft.com/en-us/ef/core/querying/related-data#related-data-and-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 without MVC, it would be:

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 3

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 4

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 5

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 6

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/