handler.cs

void Handler(InventoryAdjusted msg)
{
    using(var trx = db.BeginTransaction())
    {
        db.Execute("INSERT INTO EventConcurrency (Handler, MessageID) VALUES (@handler, @messageID)", "AdjustInventory", msg.ID);
        
        db.Execute("UPDATE Inventory SET Quantity=Quantity + @qty WHERE SKU=@sku", msg.Event.Quantity,  msg.Event.SKU);

        trx.Commit();
    }
}