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.Runtime.InteropServices;
using System.Diagnostics;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public delegate int HookProc(int nCode, int wParam, IntPtr lParam);//定义钩子过程委托（钩子函数原型）
        [DllImport("user32.dll")]
        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadID);

        //卸载钩子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern bool UnHookWindowsHookEx(int idHook);

        //调用下一个钩子
        [DllImport("user32.dll")]
        public static extern int CallNextHookEx(int idHook, int nCode, int wParam, IntPtr lParam);

        //返回当前线程ID值
        [DllImport("kernel32.dll")]
        public static extern int GetCurrentThreadId();

        //返回指定模块的句柄
        [DllImport("kernel32.dll")]
        public static extern IntPtr GetModuleHandle(string name);


        #region
        HookProc KeyBoardProcedure;

        static int hHook = 0;//钩子函数的句柄

        public const int WH_KEYBOARD = 13;



        //钩子结构函数
        public struct KeyBoardHookStruct
        {
            public int vkCode;
            public int scanCode;
            public int flags;
            public int time;
            public int dwExtraInfo;

        }



        //安装键盘钩子
        public void HookStart()
        {
            if (hHook == 0)
            {
                //实例化一个HookProc对象
                KeyBoardProcedure = new HookProc(KeyBoardHookProc);

                //创建线程钩子
                hHook = SetWindowsHookEx(WH_KEYBOARD, KeyBoardProcedure, GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName), 0);

                //如果设置线程钩子失败
                if (hHook == 0)
                {
                    HookClear();
                }
            }
        }

        //取消钩子
        public void HookClear()
        {
            bool rsetKeyboard = true;
            if (hHook != 0)
            {
                rsetKeyboard = UnHookWindowsHookEx(hHook);
                hHook = 0;
            }
            if (!rsetKeyboard)
            {
                throw new Exception("取消钩子失败!");
            }
        }

        //对截获的键盘操作的处理
        public static int KeyBoardHookProc(int nCode, int wParam, IntPtr lParam)
        {
            if (nCode >= 0)
            {
                KeyBoardHookStruct kbh = (KeyBoardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyBoardHookStruct));

                if (kbh.vkCode == 91)
                {
                    MessageBox.Show("按下WIN键");
                }
            }

            return CallNextHookEx(hHook, nCode, wParam, lParam);
        }

        #endregion

        private void Form1_Load(object sender, EventArgs e)
        {
            HookStart();//启动Hook，截获键盘事件
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            HookClear();
        }
    }
}

if (kbh.vkCode == 91 && wParam==0x100)
                {
                    MessageBox.Show("按下WIN键");
                }