using System;

using System.Text.Json;

​

​

public class Program

{

    public static void Main(string[] args)

    {

        var options = new JsonSerializerOptions{Converters = { new StringConverter() }, PropertyNameCaseInsensitive = true, };

​

        var jsonA = "{ \"something\": { \"id\": \"ex.GUID\" } }";

        var a = JsonSerializer.Deserialize<RootObject>(jsonA, options);

        Console.WriteLine(a.Something.Id);

​

        var jsonB = "{ \"something\": { \"id\": 1 } }";

        var b = JsonSerializer.Deserialize<RootObject>(jsonB, options);

        Console.WriteLine(b.Something.Id);

    }

}

​

class RootObject

{

    public Something Something { get; set; }

}

​

class Something

{

    public string Id { get; set; }

}

​

public class StringConverter : System.Text.Json.Serialization.JsonConverter<string>

{

    public override string Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

    {

        if (reader.TokenType == JsonTokenType.Number)

        {

            var stringValue = reader.GetInt32();

            return stringValue.ToString();

        }

        else if (reader.TokenType == JsonTokenType.String)

        {

            return reader.GetString();

        }

​

        throw new System.Text.Json.JsonException();

    }

​

    public override void Write(Utf8JsonWriter writer, string value, JsonSerializerOptions options)

    {

        writer.WriteStringValue(value);

    }

}