CreateNewBid.cs

public class CreateNewBid : Command<Bid>
{
    Logger logger = LogManager.GetCurrentClassLogger();
    public Guid UserId { set; private get; }
    public int LotId { set; private get; }
    public Decimal Price { set; get; }


    public override Bid Execute(IDomainContextImpl context)
    {
        Bid bid = null;
        Lot lot = null;
        var bidSuccess = false;

        using (var transaction = context.DataContext.BeginTransaction())
        {
            try
            {
                lot = new SingleLot(LotId).Execute(context.DataContext);
                if (lot.Available > 0)
                {
                    lot.Available--;
                    lot.Reserved++;
                    context.DataContext.Update<Lot>(lot);
                    bidSuccess = true;
                }

                bid = new Bid()
                    {
                        AuctionId = lot.AuctionId,
                        TimeStamp = DateTime.UtcNow,
                        IsWinningBid = bidSuccess,
                        LotId = lot.Id,
                        Price = lot.CurrentPrice == null ? lot.StartPrice : lot.CurrentPrice > Price ? lot.CurrentPrice.Value : Price,
                        UserId = UserId
                    };

                var id = context.DataContext.Insert<Bid>(bid);
                bid.Id = id.InsertedId<int>();

                transaction.Commit();
                logger.Info("Transaction Lot succesfull");
            }
            catch (Exception e)
            {
                bidSuccess = false;
                bid.IsWinningBid = false;
                transaction.Rollback();
                logger.WarnException("Updating lot unsuccesfull, bid failed, transaction rolled back", e);
            }
        }

        // communicate this update to the client
        if (bidSuccess)
        {
            context.DomainEvents.Publish<AvailableUpdatedEvent>(new AvailableUpdatedEvent() { LotId = this.LotId, NewAvailable = lot.Available });
        }

        return bid;
    }
}