private static void ChildTest1() { FriendColl friends = new FriendColl(); friends[1] = new Friend("fwq"); friends.Add(new Friend("zxc", 100)); foreach (Friend f in friends) { Console.WriteLine(f.Name + " " + f.Age); } Console.WriteLine("---------------------------------------------"); Console.WriteLine("使用yield return 返回一个枚举序列"); foreach (int ii in WithIterator()) { Console.WriteLine(ii); } var tempList = WhereListWithIterator(friends); foreach (var ss in tempList) { Console.WriteLine(ss); } Console.ReadKey(); }