public static void Main(string[] args) { EmailSender emailer1 = new EmailSender(); emailer1.TellEveryone("Hello, World!"); emailer1.TellEveryone("Bye, World"); EmailSender emailer2 = new EmailSender(); emailer2.TellEveryone("Hello, World!"); IHasStuff stuff = new HasStuff(); for (int i = 0; i < 1000000; ++i) { foreach (string value in stuff.Values) { if (value == null) { throw new ArgumentException(); } } } }