using System;

using System.Text.Json;         

​

public class Program

{

    public static void Main()

    {

        var normalJson = "{ \"updates\": [],  \"ts\": \"209\" }";

        var failedJson = "{ \"failed\": 1,  \"ts\": 30 }";

        JsonTypeGuess(normalJson);

        JsonTypeGuess(failedJson);

    }

    public static void JsonTypeGuess(string json)

    {

        var options = new JsonSerializerOptions

        {

            PropertyNameCaseInsensitive = true,

        };

        Console.WriteLine($"Processing {json}");

        var baseObj = JsonSerializer.Deserialize<BaseDto>(json, options);

        if (baseObj.Failed != 0)

        {

            Console.WriteLine("Error!");

            var errorObj = JsonSerializer.Deserialize<ErrorDto>(json, options);

            Console.WriteLine(JsonSerializer.Serialize(errorObj));

        }

        else

        {

            Console.WriteLine("OK!");

            var normalObj = JsonSerializer.Deserialize<NormalDto>(json, options);

            Console.WriteLine(JsonSerializer.Serialize(normalObj));

        }

    }   

}

​

public class BaseDto

{

    public int Failed { get; set; }

}

​

public class ErrorDto : BaseDto

{

    public int Ts { get; set; }

}

​

public class NormalDto : BaseDto

{

    public string Ts { get; set; }

    public object[] Updates { get; set; }

}

​

​