转载自：http://blog.csdn.net/junglesong/archive/2007/08/17/1747822.aspx

1.首先引入System.Runtime.InteropServices

 using System.Runtime.InteropServices;

2.在类内部声明两个API函数,它们的位置和类的成员变量等同.

[System.Runtime.InteropServices.DllImport("user32.dll")] //申明API函数       
        public static extern bool RegisterHotKey(
            IntPtr hWnd, // handle to window         
            int id, // hot key identifier         
            uint fsModifiers, // key-modifier options        
            Keys vk // virtual-key code           
            );

[System.Runtime.InteropServices.DllImport("user32.dll")] //申明API函数       
        public static extern bool UnregisterHotKey(
        IntPtr hWnd, // handle to window         
        int id // hot key identifier           
        );

3.定义一个KeyModifiers的枚举,以便出现组合键

public enum KeyModifiers
    {
        None = 0,
        Alt = 1,
        Control = 2,
        Shift = 4,
        Windows = 8
    }

4.在类的构造函数出注册系统热键

示例,下例注册了四个热键:

       public MainForm()
        {
            InitializeComponent();

            RegisterHotKey(Handle, 100, 2, Keys.Left);// 热键一:Control +光标左箭头
            RegisterHotKey(Handle, 200, 2, Keys.Right);/ /热键一:Control +光标右箭头
            RegisterHotKey(Handle, 300, 2, Keys.Up);// 热键一:Control +光标上箭头
            RegisterHotKey(Handle, 400, 2, Keys.Down);// 热键一:Control +光标下箭头

            ....;
        }

5.重写WndProc()方法，通过监视系统消息，来调用过程

示例:

protected override void WndProc(ref Message m)//监视Windows消息          
        {           
            const int WM_HOTKEY = 0x0312;//如果m.Msg的值为0x0312那么表示用户按下了热键           
            switch (m.Msg)              
            {   
                case WM_HOTKEY:                      
                    ProcessHotkey(m);//按下热键时调用ProcessHotkey()函数
                break;              
            }           
           
            base.WndProc(ref m); //将系统消息传递自父类的WndProc          
        }  

5.不用说,我们接下来需要实现ProcessHotkey函数:

//按下设定的键时调用该函数          

private void ProcessHotkey(Message m)  
        {
            IntPtr id = m.WParam; //IntPtr用于表示指针或句柄的平台特定类型          
            //MessageBox.Show(id.ToString());           
            string sid = id.ToString();
            switch (sid)
            {
                case "100": DecreseVolumnb(); break;// 按下Control +光标左箭头,调用函数DecreseVolumnb(); 
                case "200": AddVolumnb(); break;// 按下Control +光标右箭头,调用函数AddVolumnb()
                case "300":// 按下Control +光标上箭头,显示窗体
                    this.Visible = true;
                    break;
                case "400":// 按下Control +光标下箭头,隐藏窗体
                    this.Visible = false;
                    break;        
            }       
        }

很明显接下来分别实现函数DecreseVolumnb(); 和AddVolumnb(); 即可.

6.最后别忘了在程序退出时取消热键的注册

private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            UnregisterHotKey(Handle, 100);//卸载第1个快捷键              
            UnregisterHotKey(Handle, 200); //缷载第2个快捷键
            UnregisterHotKey(Handle, 300);//卸载第3个快捷键              
            UnregisterHotKey(Handle, 400); //缷载第4个快捷键
        }

以上就是在C#程序中使用系统热键的整个过程