Difficulty implementing SetWindowsHookEx

[JordanAnthonyKing]

Actual behavior

Apologies if I'm misunderstanding something, documentation is rather sparse. I'm attempting to implement a low level keyboard hook in a .net 5.0 console (for now) app.

Translating from a simple C++ example:

  s_llKeyboardHook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, GetModuleHandle(NULL), NULL);
  
  static inline HHOOK s_llKeyboardHook = nullptr;
  
  static LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
  {
      /* Some code */
      return CallNextHookEx(NULL, nCode, wParam, lParam);
  }

To C#:

class Program

{
  static ManualResetEvent _quitEvent = new ManualResetEvent(false);
  
  static void Main(string[] args)
  {
	  Console.CancelKeyPress += (sender, eArgs) =>
	  {
		  _quitEvent.Set();
		  eArgs.Cancel = true;
	  };
  
	  using SafeHandle handle = PInvoke.SetWindowsHookEx(SetWindowsHookEx_idHook.WH_KEYBOARD_LL, HookProc, PInvoke.GetModuleHandle((string)null), 0);
  
	  _quitEvent.WaitOne();
	  handle.Close();
  }
  
  static LRESULT HookProc(int nCode, WPARAM wParam, LPARAM lParam)
  {
	  System.Diagnostics.Debug.WriteLine("Hello World!");
	  
	  return PInvoke.CallNextHookEx(null, nCode, wParam, lParam);
  }
}

Attempting to use PInvoke.GetModuleHandle((string)null), gives the error: CS1503 Argument 3: cannot convert from 'nint' to 'System.Runtime.InteropServices.SafeHandle'

I've seen a few more involved examples than this, and some where just null is provided in place of a handler but following any of these has resulted in the HookProc not being called.

I believe this is related to microsoft/win32metadata#147 but couldn't find a workaround in the thread.

What is the correct way to go about this?

Expected behavior

A way to use GetModuleHandle in SetWindowsHookEx, or a working alternative.

Repro steps

1. NativeMethods.txt content:

CreateFile
SetWindowsHookEx
GetModuleHandle
CallNextHookEx
MarshallAs

2. Create a new .net 5.0 console app
3. Paste the code as given into Program.cs

Context

• CsWin32 version: 0.4.422-beta
• Target Framework: .net 5.0

[AraHaan]

Cant you pass in null directly without casting to (string)?

Also why use GetModuleHandle(null); over something like the way to get the handle to the executing assembly and using that from the BCL itself?

[JordanAnthonyKing]

Cant you pass in null directly without casting to (string)?

Passing in null without casting is ambiguous.

Also why use GetModuleHandle(null); over something like the way to get the handle to the executing assembly and using that from the BCL itself?

Most of this is pretty new to me, I've fiddled with this stuff a little via Power Toys, mostly I just want to get the hook set up and then code away as normal in C#. I attempted briefly writing a basic SafeHandle that would just return false for isInvalid and seeing what would happen ala this example from microsoft/win32metadata#147 but no luck getting any output.

  _hCtrl = PInvoke.CreateWindowEx(Constants.WS_EX_NOPARENTNOTIFY,
      "Button",
      "&Settnigs",
      Constants.WS_TABSTOP | Constants.WS_VISIBLE | Constants.WS_CHILD | Constants.WS_GROUP,
      10, 10, 88, 24, _hDlg,
      new DestroyMenuSafeHandle((IntPtr) 3, false),
      new FreeLibrarySafeHandle(PInvoke.GetModuleHandle((string)null), false),
      null);

[AArnott]

Your problem may not be the interop at all. Maybe it's because the way the callback is invoked is via the Windows message pump, and your console app doesn't have one.

[JordanAnthonyKing]

Your problem may not be the interop at all. Maybe it's because the way the callback is invoked is via the Windows message pump, and your console app doesn't have one.

Thank you for the answer. I will look into this.