How to set a window hook in other application?

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 笔记本hook
{
    public partial class Form1 : Form
    {
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)] 
    private static extern IntPtr GetModuleHandle(string lpModuleName);
        [DllImport("kernel32", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        private static extern  int GetCurrentThreadId ();
        [DllImport("User32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        private static extern int GetWindowThreadProcessId(IntPtr hwnd, out int ID);
        [DllImport("User32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
        public static extern bool SetForegroundWindow(IntPtr hWnd);
        [DllImport("kernel32", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern IntPtr OpenProcess(uint fdwAccess,bool fInherit,uint IDProcess);
        [DllImport("kernel32", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern IntPtr VirtualAllocEx(IntPtr hProcess,int lpAddress,int dwSize,int flAllocationType,int flProtect);


        

        public Form1()
        {
            InitializeComponent();
        }
      static int hHook = 0;

        const int WH_KEYBOARD = 13;
        const int PROCESS_ALL_ACCESS = 0x1F0FFF;
       // const int PROCESS_VM_READ = 0x0010;
       // const int PROCESS_VM_WRITE = 0x0020;     
        [StructLayout(LayoutKind.Sequential)]
        public class KeyboardHookStruct
        {
            public int vkCode; 
            public int scanCode; 
            public int flags;
            public int time;
            public int dwExtraInfo;
        }
        public void HOOK_Start()
        {
            if (hHook == 0)
            {
                IntPtr hWnd = NativeMethods.FindWindow(null, "Internet Explorer");
                NativeMethods.HookProc hp = new NativeMethods.HookProc(KbHookProc);
                int outId; int pId;
                hHook = NativeMethods.SetWindowsHookEx(2,
                    hp,
                  IntPtr.Zero,
                   GetWindowThreadProcessId(hWnd, out outId));

                if (hHook == 0)
                {
                    MessageBox.Show("dead start");
                    toolStripStatusLabel1.Text = "dead start";
                    return;
                }
                else toolStripStatusLabel1.Text = "success!";
            }
        }
        private void button1_Click(object sender, EventArgs e)
        {
            HOOK_Start();
        }
        void UnHook()
        {
            if (hHook > 0)
            {
                bool ret = NativeMethods.UnhookWindowsHookEx(hHook);

                if (ret == false)
                {
                    MessageBox.Show("failed!");
                    return;
                }

                hHook = 0;
               toolStripStatusLabel1.Text="failed";
            }
        }

        public static int KbHookProc(int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode < 0)
            {
                return NativeMethods.CallNextHookEx(hHook, nCode, wParam, lParam);
            }
            else
            {
                int r =  NativeMethods.CallNextHookEx(hHook, nCode, wParam, lParam);

                if (wParam == (IntPtr)256)
                {
                }
                else
                {
                    KeyboardHookStruct MyKeyboardHookStruct = (KeyboardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyboardHookStruct));

                    MessageBox.Show(MyKeyboardHookStruct.vkCode.ToString());
                }

return r;
            }
        }
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            UnHook();
        }
internal static class NativeMethods
    {
        public delegate int HookProc(int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("user32.dll", EntryPoint = "FindWindow", SetLastError = true, CharSet = CharSet.Unicode)]
        internal static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern bool UnhookWindowsHookEx(int idHook);

        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern int CallNextHookEx(int idHook, int nCode, IntPtr wParam, IntPtr lParam); 
        }

private void button2_Click(object sender, EventArgs e)
{
    UnHook();
}
    }
}