Yes in this case a engine_frame() call should be equivalent to wait(1). I just tried to use hwnd and you are right, there seems to be a problem, because hwnd seems to be always 0. I'll look into that right now ^^

get the C# wrapper:
for A7.85.4 and A8.30.4, Version 2.3.9
at http://acknexwrapper2.matthias-auer.net/ or visit the thread