MiddleModule：

using System;
using System.Collections.Generic;
using System.Text;

namespace Observer
{
    /// <summary>
    /// 定义发布消息的委托
    /// </summary>
    /// <param name="sender">发布者</param>
    /// <param name="msg">消息</param>
    public delegate void Send(object sender, object msg);
    /// <summary>
    /// 观察者的中间模块组建
    /// </summary>
    public class MiddleModule
    {
        /// <summary>
        ///消息发布的事件
        /// </summary>
        public static event Send eventSend;

        public static void SendMessage(object sender, object msg)
        {
            if (eventSend != null)
            {
                eventSend(sender, msg);
            }
        }
    }
}

 
  
 namespace WinObserver 
 { 
     public partial class FrmMain : Form 
     { 
         ///  <summary> 
         /// 构造方法，在构造主窗体的时候就订阅来自FrmChild1的消息 
         ///  </summary> 
         public FrmMain() 
         { 
             InitializeComponent(); 
             MiddleModule.eventSend += new Send(MiddleModule_eventSend); 
         } 
  
         ///  <summary> 
         /// 接收FrmChild1的回传数据 
         ///  </summary> 
         ///  <param name="sender"> </param> 
         ///  <param name="msg"> </param> 
         void MiddleModule_eventSend(object sender, object msg) 
         { 
             FrmChild1 frmChild1 = sender as FrmChild1; 
             if (null != frmChild1) 
             { 
                 this.lblMsg.Text = "FrmChild1的回传数据："+msg.ToString(); 
             } 
         } 
  
         private void btnShow1_Click(object sender, EventArgs e) 
         { 
             FrmChild1 frmChild1 = FrmChild1.CreateInstance(); 
             frmChild1.Show(); 
         } 
  
         private void btnShow2_Click(object sender, EventArgs e) 
         { 
             FrmChild2 frmChild2 = FrmChild2.CreateInstance(); 
             frmChild2.Show(); 
         } 
  
         private void btnSend_Click(object sender, EventArgs e) 
         { 
             //由Observer模块传递数据 
             if (String.IsNullOrEmpty(this.txtMsg.Text)) 
             { 
                 MiddleModule.SendMessage(this, String.Empty); 
             } 
             else 
     &nb