i just uploaded a new version of the wrapper : 1.1.1.3 get it here : http://acknexwrapper.matthias-auer.net
Fixes bug where assigning null to an EngineObject parameter caused an exception.

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