1.cs

namespace Fohjin.DDD.Events.Account
{
    [Serializable]
    public class CashWithdrawnEvent : DomainEvent
    {
        public decimal Balance { get; private set; }
        public decimal Amount { get; private set; }

        public CashWithdrawnEvent(decimal balance, decimal amount)
        {
            Balance = balance;
            Amount = amount;
        }
    }

    [Serializable]
    public class CashWithdrawnEvent_v2 : DomainEvent
    {
        public decimal Balance { get; private set; }
        public decimal Amount { get; private set; }
        public Guid AtmId { get; private set; }

        public CashWithdrawnEvent_v2(decimal balance, decimal amount, Guid atmId)
        {
            Balance = balance;
            Amount = amount;
            AtmId = atmId;
        }
    }
}

2.cs

namespace Test.Fohjin.DDD.Spike
{
    public class Spike_test_1 : BaseTestFixture
    {
        private object ConvertedEvent;

        protected override void When()
        {
            ConvertedEvent = new EventConvertor().Convert(new CashWithdrawnEvent(10.0M, 20.0M));
        }

        [Then]
        public void The_converted_event_is_the_latest_version()
        {
            ConvertedEvent.WillBeOfType<CashWithdrawnEvent_v4>();
        }

        [Then]
        public void The_converted_event_wil_contain_the_correct_data()
        {
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Balance.WillBe(10.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Amount.WillBe(20.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().AtmId.WillBe(string.Empty);
        }
    }

    public class Spike_test_2 : BaseTestFixture
    {
        private object ConvertedEvent;

        protected override void When()
        {
            ConvertedEvent = new EventConvertor().Convert(new CashWithdrawnEvent_v2(10.0M, 20.0M, "12345"));
        }

        [Then]
        public void The_converted_event_is_the_latest_version()
        {
            ConvertedEvent.WillBeOfType<CashWithdrawnEvent_v4>();
        }

        [Then]
        public void The_converted_event_wil_contain_the_correct_data()
        {
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Balance.WillBe(10.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Amount.WillBe(20.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().AtmId.WillBe("12345");
        }
    }

    public class Spike_test_3 : BaseTestFixture
    {
        private object ConvertedEvent;

        protected override void When()
        {
            ConvertedEvent = new EventConvertor().Convert(new CashWithdrawnEvent_v3(10.0M, 20.0M, "12345"));
        }

        [Then]
        public void The_converted_event_is_the_latest_version()
        {
            ConvertedEvent.WillBeOfType<CashWithdrawnEvent_v4>();
        }

        [Then]
        public void The_converted_event_wil_contain_the_correct_data()
        {
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Balance.WillBe(10.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Amount.WillBe(20.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().AtmId.WillBe("12345");
        }
    }

    public class Spike_test_4 : BaseTestFixture
    {
        private object ConvertedEvent;

        protected override void When()
        {
            ConvertedEvent = new EventConvertor().Convert(new CashWithdrawnEvent_v4(10.0M, 20.0M, "12345"));
        }

        [Then]
        public void The_converted_event_is_the_latest_version()
        {
            ConvertedEvent.WillBeOfType<CashWithdrawnEvent_v4>();
        }

        [Then]
        public void The_converted_event_wil_contain_the_correct_data()
        {
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Balance.WillBe(10.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().Amount.WillBe(20.0M);
            ConvertedEvent.As<CashWithdrawnEvent_v4>().AtmId.WillBe("12345");
        }
    }
}

3.cs

namespace Test.Fohjin.DDD.Spike
{
    public class EventConvertor
    {
        private readonly Dictionary<Type, Func<object, object>> _convertors;

        public EventConvertor()
        {
            _convertors = new Dictionary<Type, Func<object, object>>();
            RegisterEventConvertors();
        }

        private void RegisterEventConvertors()
        {
            _convertors.Add(typeof(CashWithdrawnEvent), x => new CashWithdrawnEventConvertor().Convert((CashWithdrawnEvent)x));
            _convertors.Add(typeof(CashWithdrawnEvent_v2), x => new CashWithdrawnEvent_v2Convertor().Convert((CashWithdrawnEvent_v2)x));
            _convertors.Add(typeof(CashWithdrawnEvent_v3), x => new CashWithdrawnEvent_v3Convertor().Convert((CashWithdrawnEvent_v3)x));
        }

        public object Convert(object soureEvent)
        {
            Func<object, object> convertor;
            return _convertors.TryGetValue(soureEvent.GetType(), out convertor) 
                ? Convert(convertor(soureEvent)) 
                : soureEvent;
        }
    }

    public interface IEventConvertor<TSourceEvent, TTargetEvent>
        where TSourceEvent : IDomainEvent
        where TTargetEvent : IDomainEvent
    {
        TTargetEvent Convert(TSourceEvent sourceEvent);
    }

    public class CashWithdrawnEventConvertor : IEventConvertor<CashWithdrawnEvent, CashWithdrawnEvent_v4>
    {
        public CashWithdrawnEvent_v4 Convert(CashWithdrawnEvent sourceEvent)
        {
            var theEvent = new CashWithdrawnEvent_v4(sourceEvent.Balance, sourceEvent.Amount, string.Empty)
            {
                AggregateId = sourceEvent.AggregateId
            };
            (theEvent as IDomainEvent).Version = (sourceEvent as IDomainEvent).Version;
            return theEvent;
        }
    }

    public class CashWithdrawnEvent_v2Convertor : IEventConvertor<CashWithdrawnEvent_v2, CashWithdrawnEvent_v3>
    {
        public CashWithdrawnEvent_v3 Convert(CashWithdrawnEvent_v2 sourceEvent)
        {
            var theEvent = new CashWithdrawnEvent_v3(sourceEvent.Balance, sourceEvent.Amount, sourceEvent.AtmId)
            {
                AggregateId = sourceEvent.AggregateId
            };
            (theEvent as IDomainEvent).Version = (sourceEvent as IDomainEvent).Version;
            return theEvent;
        }
    }

    public class CashWithdrawnEvent_v3Convertor : IEventConvertor<CashWithdrawnEvent_v3, CashWithdrawnEvent_v4>
    {
        public CashWithdrawnEvent_v4 Convert(CashWithdrawnEvent_v3 sourceEvent)
        {
            var theEvent = new CashWithdrawnEvent_v4(sourceEvent.Balance, sourceEvent.Amount, sourceEvent.AtmId)
            {
                AggregateId = sourceEvent.AggregateId
            };
            (theEvent as IDomainEvent).Version = (sourceEvent as IDomainEvent).Version;
            return theEvent;
        }
    }
}