Posting Dictionary<string, object> without receiving valuekind?

I'm building some generic storedproc service in blazor wasm.

So, I'm preparing object Dictionary<string, object>

 public async Task ExecProc()
{
    parameters=await this.ihttp.Post<Dictionary<string, object?>>("api/GSP/ExecProc/"+this.ProcedureName, parameters);
}

so it is for example key: 'v_str1_o' and value test like on screen values in debug when sending... and sending it to api with my params:

But when I receive it in api

[HttpPost]
[Route("ExecProc/{SPname}")]
public IActionResult ExecProc(string SPname, [FromBody] Dictionary<string, object?> parameters)

and recive it as same key but value like ValueKind = String : "test" on screenshot how it looks in debug - values with additional valuekind markup :

I know that from .net core 3.0 there is new json serializer by microsoft etc. but I don't want this valuekind stuff. I want the raw values as I sent them. Is there any way to do this without installing newtonsoft json ? I know how to do it with newtonsoft - im using same solution in some other projects, but my goal this time was to not use this library as .net has its own fast serializer / deserializer now.