public void AddItem(Item item, int amount, int price) { var existing = gameData.GetShopItem(npcInstanceId, item.Id); if (existing != null) { existing.Amount += amount; } else { var shopItem = gameData.CreateShopItem(); shopItem.NpcInstanceId = npcInstanceId; shopItem.ItemId = item.Id; shopItem.Amount = amount; shopItem.Price = price; } }