object type is showing as an empty array in .net 6

I am migrating from .netcore 2.1 to .net 6. I have an endpoint that has a return type of Task<IActionResult> I have a class that has properties of type object.
And after some checks i am returning an ok result of my object i.e return Ok(myObj);
This is working without any problems in .netcore 2.1 but in .net6 the object properties are returning empty arrays for some reason.
I created a new app directly in .net 6 and tried to replicate the issue to see if it is some mistake in I did while migrating or not but it seems that it doesn't work either. The new project looks like this :

 [HttpGet("test")]   
public IActionResult Test()
{
var features = new Dictionary<string, bool>()
{
{ "Foo", true },
{ "Bar", false }
};
var settings = new Dictionary<string, string>()
{
{ "font-size", "16-px" },
{ "showOnStartUp", "no" }
};
var resp = new Result()
{
InnerDto = new InnerDto()
{
Foo = BuildObject(features.Select(f => new KeyValuePair<string, object>(f.Key, f.Value)).ToDictionary(k => k.Key, v => v.Value)),
Bar = BuildObject(settings.Select(f => new KeyValuePair<string, object>(f.Key, f.Value)).ToDictionary(k => k.Key, v => v.Value))
},
S = "Test"
};
return Ok(resp);
}
private static object BuildObject(Dictionary<string, object> foo)
{
var objects = foo.Select(f => new
{
Key = f.Key,
Value = SetSettingsValueBasedOnType(f)
}).ToList();
var sb = new StringBuilder();
sb.AppendLine("{");
for (int i = 0; i < objects.Count; i++)
{
string val;
var obj = objects[i];
if (bool.TryParse(obj.Value.ToString(), out var parsedVal))
{
val = obj.Value.ToString()!.ToLower();
}
else
{
val = JsonConvert.SerializeObject(obj.Value);
}
var line = $@"""{obj.Key}"":{val}";
sb.AppendLine(line);
if (i < objects.Count - 1)
{
sb.Append(',');
}
}
sb.AppendLine("}");
var featuresObj = JsonConvert.DeserializeObject(sb.ToString());
return featuresObj!;
}
private static object SetSettingsValueBasedOnType(KeyValuePair<string, object> bar)
{
object val;
if (bool.TryParse(bar.Value.ToString(), out var parseVal))
{
val = parseVal;
}
else
{
val = bar.Value;
}
return val;
}
}
public class Result
{
public string S { get; set; }
public InnerDto InnerDto { get; set; }
}
public class InnerDto
{
public object Foo { get; set; }
public object Bar { get; set; }
}

the logic is working to last line before the return ok as you can see here:

and the response I'm getting is like this:

What is making this work on .netcore 2.1 and not on .net 6 ?

if you are using Newtonsoft.JSON, it is fine, just add serialize object to your object.

Change this

return Ok(resp);

to

return Ok(JsonConvert.SerializeObject(resp, Formatting.Indented));

Now we know it works, we could add it globally to all controllers by doing this:

builder.Services.AddControllers()
.AddNewtonsoftJson();

In this case, you might need to install the following package:

<PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="6.0.13" />

Then this will also work return Ok(resp);

And here is your output:

Microsoft doc: https://learn.microsoft.com/en-us/dotnet/api/microsoft.extensions.dependencyinjection.newtonsoftjsonmvcbuilderextensions.addnewtonsoftjson?view=aspnetcore-6.0