Разобрать код АнтиКейлоггера: проблема с SetWindowsHookEx()

using System;
using System.Net;
using System.Net.Mail;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.IO;
 
 
namespace AntiKeylogger
{
    class Program
    {
        #region API
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook, DebugProc lpfn, IntPtr hMod, uint dwThreadId);
 
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);
 
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);
 
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);
 
        [DllImport("user32.dll", SetLastError = true)]
        static extern int GetWindowThreadProcessId(
            [In] IntPtr hWnd,
            [Out, Optional] IntPtr lpdwProcessId
            );
 
        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr GetForegroundWindow();
 
        [DllImport("user32.dll", SetLastError = true)]
        static extern ushort GetKeyboardLayout(
            [In] int idThread
            );
        #endregion
 
        static void Main(string[] args)
        {
            _hookID = SetHook(_proc);
            
            UnhookWindowsHookEx(_hookID);
            Console.ReadKey();
        }
 
        private const int WH_KEYBOARD_LL = 13;
        private const int WH_DEBUG = 9;
        private const int WM_KEYDOWN = 0x0100;
        private static DebugProc _proc = HookCallback;
        private static IntPtr _hookID = IntPtr.Zero;
        private delegate IntPtr DebugProc(int nCode, IntPtr wParam, IntPtr lParam);
        private static IntPtr SetHook(DebugProc proc)
        {
            using (Process curProcess = Process.GetCurrentProcess())
            using (ProcessModule curModule = curProcess.MainModule)
            {
                
                return SetWindowsHookEx(WH_DEBUG, proc, GetModuleHandle(curModule.ModuleName), 0);
            }
        }
        
 
        private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
        {
            
            if (nCode == 0 && wParam == (IntPtr)WM_KEYDOWN)
            {
                return (IntPtr)1;
            }
            return CallNextHookEx(_hookID, nCode, wParam, lParam);
        }
        }
    }