Repository.cs

public class ShoppingCartRepository
{
    private readonly IDbConnection _connection;

    public ShoppingCartRepository(IDbConnection connection)
    {
        _connection = connection;
    }

    public async Task<ShoppingCartEventDomain> GetShoppingCart(Guid shoppingCartId)
    {
        var shoppingCart = await _connection.QueryFirstAsync<ShoppingCart>("SELECT CustomerId FROM ShoppingCarts WHERE ShoppingCartId=@ShopingCartId",
            new {ShoppingCartId = shoppingCartId});

        var items = await _connection.QueryAsync<ShoppingCartItem>("SELECT ProductId, Quantity FROM ShoppingCartItems WHERE ShoppingCartId=@ShopingCartId",
            new {ShoppingCartId = shoppingCartId});
        shoppingCart.Items = items.ToList();

        return new ShoppingCartEventDomain(shoppingCart);
    }

    public async Task Save(ShoppingCartEventDomain shoppingCart)
    {
        var trx = _connection.BeginTransaction();
        var evnts = shoppingCart.GetEvents();
        foreach (var evnt in evnts)
        {
            if (evnt is ItemAdded itemAdded)
            {
                await ItemAdded(itemAdded, trx);
            }
            else if (evnt is QuantityIncremented quantityIncremented)
            {
                await QuantityIncremented(quantityIncremented, trx);
            }
            else if (evnt is ItemRemoved itemRemoved)
            {
                await ItemRemoved(itemRemoved, trx);
            }
        }
        trx.Commit();
    }

    private async Task ItemAdded(ItemAdded evnt, IDbTransaction trx)
    {
        await _connection.ExecuteAsync("INSERT INTO ShoppingCartItems (ShoppingCartId, ProductId, Quantity, Price) VALUES (@ShoppingCartId, @ProductId, @Quantity, @Price)",
            new
            {
                ShoppingCartId = evnt.ShoppingCartId,
                ProductID = evnt.ProductId,
                Quantity = evnt.Quantity,
                Price = evnt.Price
            }, trx);
    }

    private async Task QuantityIncremented(QuantityIncremented evnt, IDbTransaction trx)
    {
        await _connection.ExecuteAsync("UPDATE ShoppingCartItems SET Quantity=Quantity+@Quantity WHERE ShoppingCartId=@ShoppingCartId AND ProductID=@ProductId",
            new
            {
                ShoppingCartId = evnt.ShoppingCartId,
                ProductID = evnt.ProductId,
                Quantity = evnt.Quantity,
            }, trx);
    }

    private async Task ItemRemoved(ItemRemoved evnt, IDbTransaction trx)
    {
        await _connection.ExecuteAsync("DELETE FROM ShoppingCartItems WHERE ShoppingCartId=@ShoppingCartId AND ProductId=@ProductId",
            new
            {
                ShoppingCartId = evnt.ShoppingCartId,
                ProductID = evnt.ProductId
            }, trx);
    }
}