觀察者-中介者設計模式（非委托實現方式）

通過介面實現，實現松耦合。

1. 通過中介者（主窗體），子窗體1中沒有任何任何其它子窗體的信息，實現觀察者與被觀察者之間的徹底解耦。

主窗體

public partial class mainform : Form
    {
        public mainform()
        {
            InitializeComponent();
        }

        private void butMessage_Click(object sender, EventArgs e)
        {
            childform1 c1 = new childform1();
            c1.Show();
            childform2 c2 = new childform2();
            c1.messageonList.Add(c2);
            c2.Show();
            childform3 c3 = new childform3();
            c1.messageonList.Add(c3);
            c3.Show();
        }
    }

子窗體1

 public partial class childform1 : Form
    {
        public childform1()
        {
            InitializeComponent();
            messageonList = new List<ImessageOn>();
        }

        //這個集合放我們的觀察者
        public List<ImessageOn> messageonList { get; set; }

        private void butMessage_Click(object sender, EventArgs e)
        {
            foreach(var messageon in messageonList)
            {
                messageon.ReceiveMessage("小明");
            }
        }
    }

子窗體2、3

public partial class childform2 : Form,ImessageOn
    {
        public childform2()
        {
            InitializeComponent();
        }

        public void ReceiveMessage(string str)
        {
            this.textMessage.Text = str + " " + DateTime.Now.ToString();
        }
    }