internal IntPtr CriticalAttach(IntPtr hwnd)
{
if (hwnd == IntPtr.Zero)
{
throw new ArgumentNullException("hwnd");
}
if (_bond != Bond.Unattached)
{
throw new InvalidOperationException();
}
NativeMethods.WndProc newWndProc = new NativeMethods.WndProc(SubclassWndProc);
IntPtr oldWndProc = UnsafeNativeMethods.GetWindowLongPtr(new HandleRef(this, hwnd), NativeMethods.GWL_WNDPROC);
HookWindowProc(hwnd, newWndProc, oldWndProc);
// Return the GC handle as a unique identifier of this
return((IntPtr)_gcHandle);
}