1. 在需要进行序列化和反序列化的类中，添加JsonConverterAttribute，指定JsonConverter类型为JsonSubtypes。例如：

[JsonConverter(typeof(JsonSubtypes))]
public abstract class Shape
{
    public int Id { get; set; }
    public abstract double Area { get; }
}

public class Circle : Shape
{
    public double Radius { get; set; }
    public override double Area => Math.PI * Radius * Radius;
}

public class Square : Shape
{
    public double SideLength { get; set; }
    public override double Area => SideLength * SideLength;
}

2. 在JsonSubtypes中添加子类型和对应的类型鉴别器值。例如：

public class JsonSubtypes : JsonConverter
{
    private readonly Type[] _subtypes;
    private readonly string _discriminatorProperty;

    public JsonSubtypes()
    {
        _subtypes = new[]
        {
            typeof(Circle),
            typeof(Square),
        };
        _discriminatorProperty = "shapeType";
    }

    public override void WriteJson(JsonWriter writer, Shape value, JsonSerializer serializer)
    {
        writer.WriteStartObject();
        writer.WritePropertyName(_discriminatorProperty);
        writer.WriteValue(GetDiscriminatorValue(value));
        writer.WritePropertyName("id");
        writer.WriteValue(value.Id);
        writer.WritePropertyName("area");
        writer.WriteValue(value.Area);
        writer.WriteEndObject();
    }

    public override Shape ReadJson(JsonReader reader, Type objectType, Shape existingValue, bool hasExistingValue, JsonSerializer serializer)
    {
        JObject jObject = JObject.Load(reader);
        JToken discriminatorValue = jObject.GetValue(_discriminatorProperty, StringComparison.OrdinalIgnoreCase);
        Type type = _subtypes.FirstOrDefault(t => GetDiscriminatorValue((Shape)Activator.CreateInstance(t)) == discriminatorValue.ToString());
        if (type == null)
        {
            throw new InvalidOperationException($"Unknown {nameof(Shape)} type: {discriminatorValue}");
        }
        return (Shape)jObject.ToObject(type);
    }

    private string GetDiscriminatorValue(Shape shape)
    {
        return shape switch
        {
            Circle _ => "circle",
            Square _ => "square",
            _ => throw new InvalidOperationException($"Unknown {nameof(Shape)} type: {shape.GetType().Name}"),
        };
    }
}

3. 在需要序列化的对象上使用JsonSerializerSettings，指定Converters为一个JsonConverter的列表，将JsonSubtypes添加到列表中。例如：

var circle = new Circle { Id = 1, Radius = 5 };
var square = new Square { Id = 2, SideLength = 10