using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.ComponentModel;

namespace Testhook
{
    static class TestHook{
        [STAThread]
            static void Main(string[] args)
            {
                Application.Run(new MainForm());
            }
    }

    class MainForm : Form{
        public delegate int HookHandler(int code, IntPtr message, IntPtr state);

        [DllImport("user32.dll", SetLastError = true)]
            public static extern IntPtr SetWindowsHookEx(int hookType, HookHandler hookDelegate, IntPtr module, uint threadId);

        [DllImport("user32.dll", SetLastError = true)]
            public static extern bool UnhookWindowsHookEx(IntPtr hook);

        [DllImport("user32.dll")]
            public static extern int CallNextHookEx(IntPtr hook, int code, IntPtr message, IntPtr state);

        [StructLayout(LayoutKind.Sequential)]
            public class KBDLLHOOKSTRUCT
            {
                public uint vkCode;
                public uint scanCode;
                public KBDLLHOOKSTRUCTFlags flags;
                public uint time;
                public UIntPtr dwExtraInfo;
            }

        [Flags]
            public enum KBDLLHOOKSTRUCTFlags : uint {
                LLKHF_EXTENDED = 0x01,
                LLKHF_INJECTED = 0x10,
                LLKHF_ALTDOWN = 0x20,
                LLKHF_UP = 0x80,
            }

        HookHandler hookDelegate;
        IntPtr hook;

        public MainForm()
        {
            const int KEYBOARD_LL = 13;
            hookDelegate = new HookHandler(OnHook);
            IntPtr hMod = Marshal.GetHINSTANCE( System.Reflection.Assembly.GetExecutingAssembly().GetModules()[0]);
            hook = SetWindowsHookEx(KEYBOARD_LL, hookDelegate, hMod, 0);
            if (hook == IntPtr.Zero){
                int errorCode = Marshal.GetLastWin32Error();
                throw new Win32Exception(errorCode);
            }
        }

        protected override void OnClosing(CancelEventArgs e)
        {
            base.OnClosing(e);
            if (hook != IntPtr.Zero)
            {
                UnhookWindowsHookEx(hook);
            }
        }

        int OnHook(int nCode, IntPtr wParam, IntPtr lParam)
        {
            KBDLLHOOKSTRUCT kb = (KBDLLHOOKSTRUCT)Marshal.PtrToStructure(lParam, typeof(KBDLLHOOKSTRUCT));

            Console.WriteLine("vkCode={0}", kb.vkCode);

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