NServiceBus - Map a header value to a message property to be used in a saga

MapHeaderToPropertyBehavior.cs

using System;
using System.Threading.Tasks;
using NServiceBus;
using NServiceBus.Pipeline;

class Program
{
    static async Task Main(string[] args)
    {
        var cfg = new EndpointConfiguration("test");
        cfg.UseTransport<LearningTransport>();
        cfg.Pipeline.Register(new MapHeaderToPropertyBehavior(), "mapper");
        var instance = await Endpoint.Start(cfg);

        do
        {
            await instance.SendLocal(new MyMessage());
        } while (Console.ReadKey().Key != ConsoleKey.Escape);

        await instance.Stop();
    }
}

interface IConversation
{
    string ConversationId { get; set; }
}

class MyMessage : IConversation, IMessage
{
    public string ConversationId { get; set; }
}


class MapHeaderToPropertyBehavior : Behavior<IIncomingLogicalMessageContext>
{
    public override Task Invoke(IIncomingLogicalMessageContext context, Func<Task> next)
    {
        var msg = context.Message.Instance as IConversation;

        if (msg != null && context.Headers.TryGetValue(Headers.ConversationId, out var headerValue))
        {
            msg.ConversationId = headerValue;
        }

        return next();
    }
}

class MyHandler : IHandleMessages<MyMessage>
{
    public Task Handle(MyMessage message, IMessageHandlerContext context)
    {
        return Console.Out.WriteLineAsync(">" + message.ConversationId);
    }
}