Create a video or powerpoint presentation.
.Net assemblies can easily be decompiled by tools like
http://www.red-gate.com/products/dotnet-development/reflector/[
^].
Even if you obfuscate the code, breaking a reasonable "protection" mechanism seems to be quite easy for those who put their mind to it.
Steinberg has tried really hard to protect their software (cubase and friends). Did it help?
It's either that or trust that the majority of the users is honest, and implement a simple protection mechanism.
Regards
Espen Harlinn