Basket.cs

public async Task TransferBasketAsync(string anonymousId, string userName)
    {
        Guard.Against.NullOrEmpty(anonymousId, nameof(anonymousId));
        Guard.Against.NullOrEmpty(userName, nameof(userName));
        var anonymousBasketSpec = new BasketWithItemsSpecification(anonymousId);
        var anonymousBasket = await _basketRepository.GetBySpecAsync(anonymousBasketSpec);
        if (anonymousBasket == null) return;
        var userBasketSpec = new BasketWithItemsSpecification(userName);
        var userBasket = await _basketRepository.GetBySpecAsync(userBasketSpec);
        if (userBasket == null)
        {
            userBasket = new Basket(userName);
            await _basketRepository.AddAsync(userBasket);
        }
        foreach (var item in anonymousBasket.Items)
        {
            userBasket.AddItem(item.CatalogItemId, item.UnitPrice, item.Quantity);
        }
        await _basketRepository.UpdateAsync(userBasket);
        await _basketRepository.DeleteAsync(anonymousBasket);
    }