Customer

public class Customer : DomainEntity 
{
    public decimal AccountBalance { get; private set; }
    public IReadOnlyList<Orders> Orders { get { return _orders.ToReadOnlyList();} }
    public string Name { get; private set; }
    
    protected Customer() {}
    
    public Customer(string name, decimal openingBalance) 
    {
        if (openingBalance < 0)
            throw new NoFreeloadersAllowedException();
        
        RaiseEvent(new CustomerCreated(name,openingBalance))
    }
    
    public void AddMoney(decimal amountToAdd)
    {
        RaiseEvent(new CustomerAddedMoney(amountToAdd))
    }
    
    public void PlaceOrder(string iceCreamFlavor, decimal price) 
    {
        if (AccountBalance >= price)
        {
            AccountBalance-=price;
            Orders.Add(new Order { Flavor = iceCreamFlavor });
            return;
        }
        
        throw new InsufficientFundsException();
    }
}

public class Order
{
    public string Flavor { get; set; }
}

Events

public sealed class CustomerCreated 
{
    public string Name { get; private set;}
    public decimal OpeningBalance { get; private set;}
    
    public CustomerCreated(string name, decimal openingBalance)
    {
        Name = name;
        OpeningBalance = openingBalance;
    }
}
public sealed class CustomerAddedMoney 
{
    public decimal Amount { get; private set;}
    
    public CustomerAddedMoney(decimal amount)
    {
        Amount = amount;
    }
}