public partial class Form1 : Form
{public Form1(){InitializeComponent();this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseDown1);this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseDown2);}private void Form1_MouseDown1(object sender, System.Windows.Forms.MouseEventArgs e){if (e.Button == System.Windows.Forms.MouseButtons.Left)System.Windows.Forms.MessageBox.Show("消息被Form1_MouseDown1函数响应");}private void Form1_MouseDown2(object sender, System.Windows.Forms.MouseEventArgs e){if (e.Button == System.Windows.Forms.MouseButtons.Left)System.Windows.Forms.MessageBox.Show("消息被Form1_MouseDown2函数响应");}
}

//
// 摘要:
//     当鼠标指针位于控件上并按下鼠标键时发生。
public event MouseEventHandler MouseDown;// 摘要:
//     表示将处理窗体、控件或其他组件的 MouseDown、MouseUp 或 MouseMove 事件的方法。
//
// 参数:
//   sender:
//     事件源。
//
//   e:
//     包含事件数据的 System.Windows.Forms.MouseEventArgs。
public delegate void MouseEventHandler(object sender, MouseEventArgs e);

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;namespace WindowsFormsApplication1
{/// <summary>/// 实现消息过滤器接口/// </summary>public class CLButtonDownFilter : IMessageFilter{public bool PreFilterMessage(ref Message m){if (m.Msg == 0x0201) // WM_LBUTTONDOWN
            {System.Windows.Forms.MessageBox.Show("App中鼠标左键按下");// 返回值为true， 表示消息已被处理，不要再往后传递，因此消息被截获// 返回值为false，表示消息未被处理，需要再往后传递，因此消息未被截获return true;}return false;}}public partial class Form1 : Form{public Form1(){InitializeComponent();// 安装自定义消息过滤器CLButtonDownFilter MyFilter = new CLButtonDownFilter();Application.AddMessageFilter(MyFilter);this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseDown1);this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseDown2);}private void Form1_MouseDown1(object sender, System.Windows.Forms.MouseEventArgs e){if (e.Button == System.Windows.Forms.MouseButtons.Left)System.Windows.Forms.MessageBox.Show("消息被Form1_MouseDown1函数响应");}private void Form1_MouseDown2(object sender, System.Windows.Forms.MouseEventArgs e){if (e.Button == System.Windows.Forms.MouseButtons.Left)System.Windows.Forms.MessageBox.Show("消息被Form1_MouseDown2函数响应");}/// <summary>/// 通过覆盖基类的窗体函数拦截消息/// </summary>/// <param name="e"></param>protected override void WndProc(ref System.Windows.Forms.Message e){//如果需要截获消息，//if(e.Msg==0x0201)// WM_LBUTTONDOWN// System.Windows.Forms.MessageBox.Show("消息被WndProc函数响应");//else// base.WndProc(ref e);//不需要截获消息则为if (e.Msg == 0x0201)// WM_LBUTTONDOWNSystem.Windows.Forms.MessageBox.Show("消息被WndProc函数响应");base.WndProc(ref e);}/// <summary>/// 通过覆盖基类的事件引发函数拦截消息/// </summary>/// <param name="e"></param>protected override void OnMouseDown(MouseEventArgs e){if (e.Button == System.Windows.Forms.MouseButtons.Left)System.Windows.Forms.MessageBox.Show("消息被OnMouseDown函数响应");//如果需要截获消息，可将base.OnMouseDown(e);语句注释掉base.OnMouseDown(e);}}
}