controlapp/ControlApp/LockKeyboard.cs

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

namespace ControlApp;

internal class LockKeyboard
{
	private delegate nint LowLevelKeyboardProc(int nCode, nint wParam, nint lParam);

	private const int WH_KEYBOARD_LL = 13;

	private static LowLevelKeyboardProc _proc = HookCallback;

	private static nint _hookID = IntPtr.Zero;

	[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
	private static extern nint SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, nint hMod, uint dwThreadId);

	[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private static extern bool UnhookWindowsHookEx(nint hhk);

	[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
	private static extern nint CallNextHookEx(nint hhk, int nCode, nint wParam, nint lParam);

	[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
	private static extern nint GetModuleHandle(string lpModuleName);

	private static nint SetHook(LowLevelKeyboardProc proc)
	{
		using Process curProcess = Process.GetCurrentProcess();
		using ProcessModule curModule = curProcess.MainModule;
		return SetWindowsHookEx(13, proc, GetModuleHandle(curModule.ModuleName), 0u);
	}

	private static nint HookCallback(int nCode, nint wParam, nint lParam)
	{
		if (nCode >= 0)
		{
			return 1;
		}
		return CallNextHookEx(_hookID, nCode, wParam, lParam);
	}

	public void Lock()
	{
		_hookID = SetHook(_proc);
	}

	public void Unlock()
	{
		UnhookWindowsHookEx(_hookID);
	}
}