ThreadPool Callback threw an unhandled exception of type Newtonsoft.Json.JsonSerializationException window.Module.s.printErr @ blazor.webassembly.js:1

Question

I had a problem when migrating from .NET CORE 5 to .NET CORE 6. I was using Newtonsoft.Json to serialize information in the backend and deserialize the data in the front end. I was using a Tuple object like this to serialize the data:

var content = new Tuple<MainConfiguration, SecondaryConfiguration>(mainConfiguration,secondaryConfiguration);
var serializedContent = JsonConvert.SerializeObject(content);

And was using this code to deserialize the data:

var data = JsonConvert.DeserializeObject<Tuple<MainConfiguration, SecondaryConfiguration>>(serializedContent ?? string.Empty);

With .NET CORE 5 it worked great in development and release.

However after migrating to .NET CORE 6 it only worked in development and not in release. Using Visual Studio everything worked fine, but when publishing the project and executing the published code, I started getting this error message in the Browser console:

ThreadPool Callback threw an unhandled exception of type Newtonsoft.Json.JsonSerializationException
window.Module.s.printErr @ blazor.webassembly.js:1

After reading a lot without results I found the answer here in the comment from v-milindm on May 26. 2022: https://github.com/dotnet/aspnetcore/issues/41748

The problem was the Tuple object, somehow the deserialization was no longer working.

The solution was simple, create an own Tuple object like this:

public class ConfigurationTuple
{

    public ConfigurationTuple() { }

    public ConfigurationTuple(MainConfiguration item1, SecondaryConfiguration item2)
    {
        Item1 = item1;
        Item2 = item2;
    }

    public MainConfiguration Item1 { get; set; }
    public SecondaryConfiguration Item2 { get; set; }

}

And then replace the .NET Tuple object with my own for serialization:

var content = new ConfigurationTuple(mainConfiguration,secondaryConfiguration);
 var serializedContent = JsonConvert.SerializeObject(content);

And in the deserialization:

var data = JsonConvert.DeserializeObject<ConfigurationTuple>(serializedContent ?? string.Empty);

Summary: When migrating from .NET Core 5 to .NET Core 6 and when using Newtonsoft.Json to serialize/deserialize content between the Frontend and Backend, DO NOT USE .NET Tuple object, create your own tuple.

The problem lies in the Front End, not the backend.

Answer 1

This question was created with the sole pourpose of helping others avoid the problem I was having.