class Person
    {
        public string Name;
        public int age;
        public Person[] Friends;
        /// <summary>
        /// 说话的方法
        /// </summary>
        /// <param name="str"></param>
        public void Speak(string str)
        {
            Console.WriteLine($"{Name}说{str}");
        }
        public bool isadult()
        {
            
            return age >=18;
        }
        public void AddFriends(Person p)
        {
            if (Friends == null)
            {
                Friends = new Person[] { p };
            }
            else
            {
                Person[] Newfriends = new Person[Friends.Length + 1];
                for (int i = 0; i < Friends.Length; i++)
                {
                    Newfriends[i] = Friends[i];
                }
                Newfriends[Newfriends.Length - 1] = p;
                Friends = Newfriends;
            }
        }
        
    }

这里复习一下Friends = Newfriends;这句并非把新数组赋值给原来的数组,而是把新数组引用赋值给变量Friends

Friends并非一个引用,而是储存引用的一个容器.