Callback is called,, but breaks. Commenting out p.SetupHook(); works.

gistfile1.txt

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;

namespace TestLauncherApp
{
    class Program
    {
        [StructLayout(LayoutKind.Sequential)]
        public class SecurityAttributes
        {
            public Int32 Length = 0;
            public IntPtr lpSecurityDescriptor = IntPtr.Zero;
            public bool bInheritHandle = false;

            public SecurityAttributes()
            {
                this.Length = Marshal.SizeOf(this);
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        public class StartupInfo
        {
            public Int32 cb = 0;
            public IntPtr lpReserved = IntPtr.Zero;
            public IntPtr lpDesktop = IntPtr.Zero; // MUST be Zero
            public IntPtr lpTitle = IntPtr.Zero;
            public Int32 dwX = 0;
            public Int32 dwY = 0;
            public Int32 dwXSize = 0;
            public Int32 dwYSize = 0;
            public Int32 dwXCountChars = 0;
            public Int32 dwYCountChars = 0;
            public Int32 dwFillAttribute = 0;
            public Int32 dwFlags = 0;
            public Int16 wShowWindow = 0;
            public Int16 cbReserved2 = 0;
            public IntPtr lpReserved2 = IntPtr.Zero;
            public IntPtr hStdInput = IntPtr.Zero;
            public IntPtr hStdOutput = IntPtr.Zero;
            public IntPtr hStdError = IntPtr.Zero;

            public StartupInfo()
            {
                this.cb = Marshal.SizeOf(this);
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct ProcessInformation
        {
            public IntPtr hProcess;
            public IntPtr hThread;
            public Int32 dwProcessId;
            public Int32 dwThreadId;
        }

        [Flags]
        public enum CreateProcessFlags : uint
        {
            DEBUG_PROCESS = 0x00000001,
            DEBUG_ONLY_THIS_PROCESS = 0x00000002,
            CREATE_SUSPENDED = 0x00000004,
            DETACHED_PROCESS = 0x00000008,
            CREATE_NEW_CONSOLE = 0x00000010,
            NORMAL_PRIORITY_CLASS = 0x00000020,
            IDLE_PRIORITY_CLASS = 0x00000040,
            HIGH_PRIORITY_CLASS = 0x00000080,
            REALTIME_PRIORITY_CLASS = 0x00000100,
            CREATE_NEW_PROCESS_GROUP = 0x00000200,
            CREATE_UNICODE_ENVIRONMENT = 0x00000400,
            CREATE_SEPARATE_WOW_VDM = 0x00000800,
            CREATE_SHARED_WOW_VDM = 0x00001000,
            CREATE_FORCEDOS = 0x00002000,
            BELOW_NORMAL_PRIORITY_CLASS = 0x00004000,
            ABOVE_NORMAL_PRIORITY_CLASS = 0x00008000,
            INHERIT_PARENT_AFFINITY = 0x00010000,
            INHERIT_CALLER_PRIORITY = 0x00020000,
            CREATE_PROTECTED_PROCESS = 0x00040000,
            EXTENDED_STARTUPINFO_PRESENT = 0x00080000,
            PROCESS_MODE_BACKGROUND_BEGIN = 0x00100000,
            PROCESS_MODE_BACKGROUND_END = 0x00200000,
            CREATE_BREAKAWAY_FROM_JOB = 0x01000000,
            CREATE_PRESERVE_CODE_AUTHZ_LEVEL = 0x02000000,
            CREATE_DEFAULT_ERROR_MODE = 0x04000000,
            CREATE_NO_WINDOW = 0x08000000,
            PROFILE_USER = 0x10000000,
            PROFILE_KERNEL = 0x20000000,
            PROFILE_SERVER = 0x40000000,
            CREATE_IGNORE_SYSTEM_DEFAULT = 0x80000000,
        }

        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern bool CreateProcess
        (
            String lpApplicationName,
            String lpCommandLine,
            SecurityAttributes lpProcessAttributes,
            SecurityAttributes lpThreadAttributes,
            Boolean bInheritHandles,
            CreateProcessFlags dwCreationFlags,
            IntPtr lpEnvironment,
            String lpCurrentDirectory,
            [In] StartupInfo lpStartupInfo,
            out ProcessInformation lpProcessInformation
        );

        [UnmanagedFunctionPointer(CallingConvention.StdCall, SetLastError = true)]
        delegate bool CreateProcess_Delegate(String lpApplicationName,
            String lpCommandLine,
            SecurityAttributes lpProcessAttributes,
            SecurityAttributes lpThreadAttributes,
            Boolean bInheritHandles,
            CreateProcessFlags dwCreationFlags,
            IntPtr lpEnvironment,
            String lpCurrentDirectory,
            [In] StartupInfo lpStartupInfo,
            out ProcessInformation lpProcessInformation);

        bool CreateProcess_Hook(String lpApplicationName,
            String lpCommandLine,
            SecurityAttributes lpProcessAttributes,
            SecurityAttributes lpThreadAttributes,
            Boolean bInheritHandles,
            CreateProcessFlags dwCreationFlags,
            IntPtr lpEnvironment,
            String lpCurrentDirectory,
            [In] StartupInfo lpStartupInfo,
            out ProcessInformation lpProcessInformation)
        {
            bool result = false;

            result = CreateProcess(lpApplicationName, lpCommandLine, lpProcessAttributes, lpThreadAttributes, 
                bInheritHandles, dwCreationFlags, lpEnvironment, lpCurrentDirectory, lpStartupInfo, out lpProcessInformation);
            try
            {
                // Add message to send to FileMonitor
                Console.WriteLine("IT WOKRED!!!!!!");
            }
            catch
            {
                // swallow exceptions so that any issues caused by this code do not crash target process
            }
            return result;
        }

        static void Main(string[] args)
        {
            var p = new Program();
            p.SetupHook();

             Process.Start("notepad.exe");
             Console.ReadKey();
             Console.WriteLine(Marshal.GetLastWin32Error());
        }

        private void SetupHook()
        {
            var createProcessHook = EasyHook.LocalHook.Create(
                EasyHook.LocalHook.GetProcAddress("kernel32.dll", "CreateProcessW"), 
                new CreateProcess_Delegate(CreateProcess_Hook), 
                this);


            createProcessHook.ThreadACL.SetExclusiveACL(new Int32[] { });
            Console.WriteLine("Hook Installed");
        }
    }
}