鉤子監聽鍵盤消息

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

namespace HookForm
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        // ... { GLOBAL HOOK }
        [DllImport("user32.dll")]
        static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc callback, IntPtr hInstance, uint threadId);

        [DllImport("user32.dll")]
        static extern bool UnhookWindowsHookEx(IntPtr hInstance);

        [DllImport("user32.dll")]
        static extern IntPtr CallNextHookEx(IntPtr idHook, int nCode, int wParam, IntPtr lParam);

        [DllImport("kernel32.dll")]
        static extern IntPtr LoadLibrary(string lpFileName);

        private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

        const int WH_KEYBOARD_LL = 13; // 全局LowLevel鍵盤上的掛鉤號碼
        const int WM_KEYDOWN = 0x100; // 按鍵消息

        private LowLevelKeyboardProc _proc = hookProc;

        private static IntPtr hhook = IntPtr.Zero;

        public void SetHook()
        {
            IntPtr hInstance = LoadLibrary("User32");
            hhook = SetWindowsHookEx(WH_KEYBOARD_LL, _proc, hInstance, 0);
        }

        public static void UnHook()
        {
            UnhookWindowsHookEx(hhook);
        }

        public static IntPtr hookProc(int code, IntPtr wParam, IntPtr lParam)
        {
            if (code >= 0 && wParam == (IntPtr)WM_KEYDOWN)
            {
                int vkCode = Marshal.ReadInt32(lParam);
                //////按鍵ascii
                if (vkCode.ToString() == "13")
                {
                    MessageBox.Show("按了Enter");
                }
                return (IntPtr)1;
            }
            else
                return CallNextHookEx(hhook, code, (int)wParam, lParam);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // 安裝鉤子
            SetHook();
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            //卸載鉤子
            UnHook();
        }
    }
}