Repository.cs

public class ShoppingCartDomainRepository
{
    private readonly SalesDbContext _dbContext;

    public ShoppingCartDomainRepository(SalesDbContext dbContext)
    {
        _dbContext = dbContext;
    }

    public async Task<ShoppingCartDomain> GetShoppingCart(Guid shoppingCartId)
    {
        var data = await _dbContext.ShoppingCarts
            .Include(x => x.Items)
            .SingleAsync(x => x.ShoppingCartId == shoppingCartId);

        return new ShoppingCartDomain(data);
    }

    public async Task Save()
    {
        await _dbContext.SaveChangesAsync();
    }
}