[Tutorial] Hooking API's using C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using EasyHook;

namespace msgbox
{
    public class Main : EasyHook.IEntryPoint
    {
        public LocalHook CreateHook;
        public Inj3ct0r.InjectorInterface Interface;
        Stack<String> Queue = new Stack<String>();

        public Main(RemoteHooking.IContext InContext, String InChannelName)
        {
            Interface = RemoteHooking.IpcConnectClient<Inj3ct0r.InjectorInterface>(InChannelName);
        }

        public void Run(RemoteHooking.IContext InContext, String InChannelName)
        {
            Interface.debug("Injected!!");
            try
            {
                CreateHook = LocalHook.Create(
                    LocalHook.GetProcAddress("user32.dll", "MessageBoxW"),
                    new DMessageBox(MessageBoxH),
                    this);

                CreateHook.ThreadACL.SetExclusiveACL(new Int32[] { 0 });
            }
            catch (Exception ExtInfo)
            {
                Interface.ReportException(ExtInfo);
                return;
            }

            try
            {
                while (true)
                {
                    System.Threading.Thread.Sleep(100);

                    if (Queue.Count > 0)
                    {
                        String[] Package = null;
                        lock (Queue)
                        {
                            Package = Queue.ToArray();
                            Queue.Clear();
                        }
                        Interface.debug(Package[0]);
                    }
                }
            }
            catch { }

        }


        //MB icons
        static int MB_ICONINFORMATION = (int)(0x00000040L);
        static int MB_ICONASTERISK = (int)(0x00000040L);
        static int MB_ICONQUESTION = (int)(0x00000020L);
        //MB buttons
        static int MB_OK = (int)(0x00000000L);
        static int MB_YESNO = (int)(0x00000004L);


        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        static extern int MessageBox(IntPtr hWnd, String text, String caption, int options);

        [UnmanagedFunctionPointer(CallingConvention.StdCall,
            CharSet = CharSet.Unicode,
            SetLastError = true)]

        delegate int DMessageBox(
             IntPtr hWnd,
             String text,
             String caption,
             int options
        );


        static int MessageBoxH(
            IntPtr hWnd,
            String text,
            String caption,
            int options)
        {
            Main This = (Main)HookRuntimeInfo.Callback;
            lock (This.Queue)
            {
                This.Queue.Push("Original MessageBox:\"\nhWnd:'" + hWnd + "'\nText:'" + text + "'\nCaption:'" + caption + "'\"");
            }

            if (text.Contains("Detected the application which")) // hook for HGWC if detected msgbox pop's up
            {
                return MessageBox(hWnd, text + "\nHOOKED by arkade ^^", caption, options);
            }
            else
            {
                return MessageBox(
                hWnd,
                text,
                caption,
                options);
            }

        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Diagnostics;
using System.Runtime.Remoting;
using EasyHook;

namespace Inj3ct0r
{

    public class InjectorInterface : MarshalByRefObject
    {
        public void IsInstalled()
        {
            Console.WriteLine("Injected ;).\r\n");
        }

        public void debug(String msg)
        {
            Console.Out.WriteLine("{0}\r\n", msg);
        }

        public void ReportException(Exception InInfo)
        {
            Console.WriteLine("Error:\r\n" + InInfo.ToString());
        }

    }

    class Program
    {
        static int delay = 500;
        static String ChannelName = null;
        static String process = "!explorer";
        static Process proc;

        static void Main(string[] args)
        {
            Console.Title = "Inj3ct0r";
            Console.ForegroundColor = ConsoleColor.Green;
            loadcfg();

            Console.WriteLine("Waiting for {0}...", process);

            while (Process.GetProcessesByName(process).Length == 0)
            {
                System.Threading.Thread.Sleep(delay);
            }
            proc = Process.GetProcessesByName(process)[0];


            try
            {

            RemoteHooking.IpcCreateServer<InjectorInterface>(ref ChannelName, WellKnownObjectMode.SingleCall);

            RemoteHooking.Inject(
               proc.Id,
               InjectionOptions.DoNotRequireStrongName,
               "msgbox.dll",
               "msgbox.dll",
                ChannelName);

            Console.ReadLine();

            }
            catch (Exception ExtInfo){
                Console.WriteLine("There was an error while connecting to target:\r\n{0}", ExtInfo.ToString());
            }

        }


        private static void loadcfg()
        {
            if (File.Exists("cfg.ini"))
            {
                string line = null;
                StreamReader cfg = new StreamReader(@"cfg.ini");
                while ((line = cfg.ReadLine()) != null)
                {
                    if (line.StartsWith("<proc>"))
                    {
                        process = line.Replace("<proc>", "").Replace("</proc>", "").Replace(".exe","");
                    }
                    if (line.StartsWith("<delay>"))
                    {
                        delay = Convert.ToInt32(line.Replace("<delay>", "").Replace("</delay>", ""));
                    }
                }
            }
        }
    }
}