Policy.cs

public class CreateShippingLabelSagaData : ContainSagaData
{
    public Guid OrderId { get; set; }
    public bool IsOrderPlaced { get; set; }
    public bool IsOrderBilled { get; set; }
}

public class CreateShippingLabelSaga :
    Saga<CreateShippingLabelSagaData>,
    IAmStartedByMessages<OrderPlaced>,
    IAmStartedByMessages<OrderBilled>
{
    protected override void ConfigureHowToFindSaga(SagaPropertyMapper<CreateShippingLabelSagaData> mapper)
    {
        mapper.ConfigureMapping<OrderPlaced>(message => message.OrderId).ToSaga(sagaData => sagaData.OrderId);
        mapper.ConfigureMapping<OrderBilled>(message => message.OrderId).ToSaga(sagaData => sagaData.OrderId);
    }

    public Task Handle(OrderPlaced message, IMessageHandlerContext context)
    {
        Data.IsOrderPlaced = true;
        return ProcessOrder(context);
    }

    public Task Handle(OrderBilled message, IMessageHandlerContext context)
    {
        Data.IsOrderBilled = true;
        return ProcessOrder(context);
    }

    private async Task ProcessOrder(IMessageHandlerContext context)
    {
        if (Data.IsOrderPlaced && Data.IsOrderBilled)
        {
            await context.SendLocal(new CreateShippingLabel() { OrderId = Data.OrderId });
            MarkAsComplete();
        }
    }
}