public class TimestampInterceptor : EmptyInterceptor
{
    private const string TIMESTAMP_PROPERTY = "Timestamp";

    private readonly IDomainContext domainContext;
    private readonly ISystemClock clock;

    public TimestampInterceptor(IDomainContext domainContext, ISystemClock clock)
    {
        this.domainContext = domainContext;
        this.clock = clock;
    }

    public override bool OnSave(object entity, object id, object[] state, 
        string[] propertyNames, IType[] types)
    {
        var timestampable = entity as ITimestampable;

        if(timestampable == null)
            return false;

        var timestamp = GetTimestamp(state, propertyNames);

        timestamp.CreatedDateTime = clock.Now();

        if (domainContext.DomainUser != null)
            timestamp.CreatedByStaff = domainContext.DomainUser.StaffName;

        return true;
    }

    public override bool OnFlushDirty(object entity, object id, object[] currentState, 
        object[] previousState, string[] propertyNames, IType[] types)
    {
        var timestampable = entity as ITimestampable;

        if (timestampable == null)
            return false;

        var timestamp = GetTimestamp(currentState, propertyNames);

        timestamp.UpdatedDateTime = clock.Now();

        if(domainContext.DomainUser != null)
            timestamp.UpdatedByStaff = domainContext.DomainUser.StaffName;

        return true;
    }

    private static Timestamp GetTimestamp(object[] state, string[] propertyNames)
    {
        var timestamp = state[Array.IndexOf(propertyNames, TIMESTAMP_PROPERTY)] as Timestamp;

        if( timestamp == null )
        {
            timestamp = new Timestamp();
            state[Array.IndexOf(propertyNames, TIMESTAMP_PROPERTY)] = timestamp;
        }

        return timestamp;
    }
}