Events.cs

public class ShoppingCartEventDomain
{
    private List<object> _events = new List<object>();
    private readonly ShoppingCart _shoppingCart;

    public ShoppingCartEventDomain(ShoppingCart shoppingCart)
    {
        _shoppingCart = shoppingCart;
    }

    public List<object> GetEvents()
    {
        return _events;
    }

    public void AddItem(Guid productId, int quantity, decimal price)
    {
        var existingItem = _shoppingCart.Items.SingleOrDefault(x => x.ProductId == productId);
        if (existingItem != null)
        {
            _events.Add(new QuantityIncremented
            {
                ShoppingCartId = _shoppingCart.ShoppingCartId,
                ProductId = productId,
                Quantity = quantity
            });
        }
        else
        {
            _shoppingCart.Items.Add(new ShoppingCartItem(_shoppingCart.ShoppingCartId, productId));

            _events.Add(new ItemAdded
            {
                ShoppingCartId = _shoppingCart.ShoppingCartId,
                ProductId = productId,
                Quantity = quantity,
                Price = price
            });
        }
    }

    public void RemoveItem(Guid productId)
    {
        var product = _shoppingCart.Items.SingleOrDefault(x => x.ProductId == productId);
        if (product != null)
        {
            _events.Add(new ItemRemoved
            {
                ShoppingCartId = _shoppingCart.ShoppingCartId,
                ProductId = productId,
            });
        }
    }
}

public class ItemAdded
{
    public Guid ShoppingCartId { get; set; }
    public Guid ProductId { get; set; }
    public int Quantity { get; set; }
    public decimal Price { get; set; }
}

public class ItemRemoved
{
    public Guid ShoppingCartId { get; set; }
    public Guid ProductId { get; set; }
}

public class QuantityIncremented
{
    public Guid ShoppingCartId { get; set; }
    public Guid ProductId { get; set; }
    public int Quantity { get; set; }
}