using System;

using System.Text.Json;

using System.Text.Json.Serialization;

public class Program

{

    [JsonPolymorphic(TypeDiscriminatorPropertyName = "EventType")]

    [JsonDerivedType(typeof(EventEnvelopeAlpha), typeDiscriminator: nameof(EventAlpha))]

    [JsonDerivedType(typeof(EventEnvelopeBravo), typeDiscriminator: nameof(EventBravo))]

    public class EventEnvelope

    {

        public Guid EventId { get; init; } = Guid.NewGuid();

        public string EventSource { get; init; } = "Event.Source";

        public DateTime EventDate { get; init; } = DateTime.UtcNow;

        //public EventData EventData { get; init; }

    }

    public class EventEnvelopeAlpha : EventEnvelope

    {

        public EventAlpha EventData { get; init; }

    }

    public class EventEnvelopeBravo : EventEnvelope

    {

        public EventBravo EventData { get; init; }

    }

​

​

    public abstract class EventData

    {

        public string SchemaVersion { get; init; } = "1.0";

    }

​

    public class EventAlpha : EventData

    {

        public string PropertyZulu { get; init; }

    }

​

    public class EventBravo : EventData

    {

        public string PropertyYankee { get; init; }

    }

    public static void Main()

    {

​

        var evt = new EventEnvelopeBravo

        {

            EventData = new EventBravo { PropertyYankee = "foo" }

        } as EventEnvelope;

        var serialized = JsonSerializer.Serialize(evt);

        var deserialized = JsonSerializer.Deserialize<EventEnvelope>(serialized);

        Console.WriteLine(serialized);

        if (deserialized is EventEnvelopeBravo e)

        {

            Console.WriteLine(e.EventData.PropertyYankee);

            //if (deserialized.EventData is EventBravo b)

            //  Console.WriteLine(b.PropertyYankee);

        }

    }

}