Solving Error "JsonException: A possible object cycle was detected" .NET Core

In previous article, I mentioned how to Deserialize XML string to Object in C# but in this article, I have mentioned how we can resolve error "JsonException: A possible object cycle was detected. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32." in .NET Core 3 or .NET Core 6.

Recently, I was working on a project and had to pass JSON from controller to View using AJAX call, but got this error.

An unhandled exception occurred while processing the request.
JsonException: A possible object cycle was detected. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32. Consider using ReferenceHandler.Preserve on JsonSerializerOptions to support cycles. Path: $.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.Race.RaceFiles.

Here is what I saw in browser:

And this was the code in C# .NET Core Controller

        public IActionResult GetRaceDetails(int id)
        {
            var str = new Race();
            using (var raceRepo = new RaceService(_configuration))
            {
                str = raceRepo.GetRace(id);
            }

            return Json(str);
        }

//while GetRace method is below
//
        public Race GetRace(int id)
        {
            Race race = new Race();
            using (var db = new EventManagementDatabase(_configuration))
            {
                race = db.Races.Include(a => a.RaceFiles).Where(a => a.ID == id).FirstOrDefault();
            }
            return race;
        }

As you can see and understand from the issue, there is possible cycles of "RaceFiles" and "Race" table.

To resolve this error in .NET Core 6+, I navigated to "Program.cs" and used below code

builder.Services.AddControllersWithViews()
    .AddJsonOptions(options =>
    options.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles
);

You will also need to add reference for:

using System.Text.Json.Serialization;

Just build and run, above error will be resolved.

If you are using .NET 5, then you can simply use below code in "Startup.cs"

services.AddControllers().AddJsonOptions(x =>
   x.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.Preserve);

again, we will need to add reference for 'System.Text.Json.Serialization'

If you are using .NET Core 3 or less, then you will need to Install Below Nuget Package

Microsoft.AspNetCore.Mvc.NewtonsoftJson

then in startup.cs, you can use below code to resolve above error.

public void ConfigureServices(IServiceCollection services)
 {
    ..........
    .......

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

Hope it helps.

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