C#中设置全局快捷键

using System;
using System.Text;
using System.Data;
using System.Drawing;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Collections;

namespace HotKey1
{
    public partial class Form1 : Form
     {
        public Form1()
         {
             InitializeComponent();
         }
        public delegate void HotkeyEventHandler(int HotKeyID);
        private int Hotkey1;
        public class Hotkey : System.Windows.Forms.IMessageFilter
         {
             Hashtable keyIDs = new Hashtable();
             IntPtr hWnd;

            public event HotkeyEventHandler OnHotkey;

            public enum KeyFlags
             {
                 MOD_SHIFT = 0x4,
                 MOD_WIN = 0x8
                 MOD_ALT = 0x1,
                 MOD_CONTROL = 0x2,
             }
             [DllImport("user32.dll")]
            public static extern UInt32 RegisterHotKey(IntPtr hWnd, UInt32 id, UInt32 fsModifiers, UInt32 vk);

             [DllImport("user32.dll")]
            public static extern UInt32 UnregisterHotKey(IntPtr hWnd, UInt32 id);

             [DllImport("kernel32.dll")]
            public static extern UInt32 GlobalAddAtom(String lpString);

             [DllImport("kernel32.dll")]
            public static extern UInt32 GlobalDeleteAtom(UInt32 nAtom);

            public Hotkey(IntPtr hWnd)
             {
                this.hWnd = hWnd;
                 Application.AddMessageFilter(this);
             }

            public int RegisterHotkey(Keys Key, KeyFlags keyflags)
             {
                 UInt32 hotkeyid = GlobalAddAtom(System.Guid.NewGuid().ToString());
                 RegisterHotKey((IntPtr)hWnd, hotkeyid, (UInt32)keyflags, (UInt32)Key);
                 keyIDs.Add(hotkeyid, hotkeyid);
                return (int)hotkeyid;
             }

            public void UnregisterHotkeys()
             {
                 Application.RemoveMessageFilter(this);
                foreach (UInt32 key in keyIDs.Values)
                 {
                     UnregisterHotKey(hWnd, key);
                     GlobalDeleteAtom(key);
                 }
             }

            public bool PreFilterMessage(ref System.Windows.Forms.Message m)
             {
                if (m.Msg == 0x312)
                 {
                    if (OnHotkey != null)
                     {
                        foreach (UInt32 key in keyIDs.Values)
                         {
                            if ((UInt32)m.WParam == key)
                             {
                                 OnHotkey((int)m.WParam);
                                return true;
                             }
                         }
                     }
                 }
                return false;
             }
         }

        public void OnHotkey(int HotkeyID) //Ctrl+F3隐藏窗体，再按显示窗体。http://www.xuehai.net
         {
            if (HotkeyID == Hotkey1)
             {
                if (this.Visible == true)
                    this.Visible = false;
                else
                    this.Visible = true;
             }
            else
             {
                this.Visible = false;
             }
         }

        private void Form1_Load(object sender, EventArgs e)
         {
             Hotkey hotkey;
             hotkey = new Hotkey(this.Handle);
             Hotkey1 = hotkey.RegisterHotkey(System.Windows.Forms.Keys.F3, Hotkey.KeyFlags.MOD_CONTROL);   //定义快键(Ctrl + F3)
             hotkey.OnHotkey += new HotkeyEventHandler(OnHotkey);
         }
     }
}