static void Main(string[] args) { List<decimal> decs = new List<decimal> { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; BankAccounts first = new BankAccounts(); first.on_add += n => Console.WriteLine("First add {0}",n); first +=20; BankAccounts second = new BankAccounts(); second.on_add += n => Console.WriteLine("Second add {0}", n); second += decs; first += second; Console.WriteLine("Sum of first = {0}", first.Sum()); Console.WriteLine("Sum of both = {0}", new BankAccounts().Add(first).Add(second).Sum()); Console.WriteLine("first: {0}", first.ToString()); Console.ReadKey(); }