public override void StartHook()
{
if (_started)
{
return;
}
_windowsKeyboardHookHandle = IntPtr.Zero;
_keyboardHookProc = LowLevelKeyboardProc; // we must keep alive proc, because GC is not aware about SetWindowsHookEx behaviour. If you remove this, the program will crash when the garbage collector reaps it.
_user32LibraryHandle = IntPtr.Zero;
_user32LibraryHandle = NativeApi.LoadLibrary("User32");
if (_user32LibraryHandle == IntPtr.Zero)
{
var errorCode = Marshal.GetLastWin32Error();
throw new Win32Exception(errorCode, $"Failed to load library 'User32.dll'. Error {errorCode}: {new Win32Exception(Marshal.GetLastWin32Error()).Message}.");
}
_windowsKeyboardHookHandle = NativeApi.SetWindowsHookEx(WH_KEYBOARD_LL, _keyboardHookProc, _user32LibraryHandle, 0);
if (_windowsKeyboardHookHandle == IntPtr.Zero)
{
var errorCode = Marshal.GetLastWin32Error();
throw new Win32Exception(errorCode, $"Failed to adjust keyboard hooks for '{Process.GetCurrentProcess().ProcessName}'. Error {errorCode}: {new Win32Exception(Marshal.GetLastWin32Error()).Message}.");
}
}
public override void StopHook()
{
if (!_started)
{
return;
}
if (_windowsKeyboardHookHandle == IntPtr.Zero)
{
return;
}
if (!NativeApi.UnhookWindowsHookEx(_windowsKeyboardHookHandle))
{
var errorCode = Marshal.GetLastWin32Error();
throw new Win32Exception(errorCode, $"Failed to remove keyboard hooks for '{Process.GetCurrentProcess().ProcessName}'. Error {errorCode}: {new Win32Exception(Marshal.GetLastWin32Error()).Message}.");
}
_windowsKeyboardHookHandle = IntPtr.Zero;
// ReSharper disable once DelegateSubtraction
_keyboardHookProc -= LowLevelKeyboardProc;
}
