Hi Nim,
What do you mean by inject.
If you want to use a dll written in c++ form c# code go ahead use P\Invoke
and DllImport attribute. But don't forget that you can use only plain
c-style functions or global c++ function if you check the exact spelling of
the fuction name (c++ decorates function names).
If you want to use classes you can do it only with COM.
If you want to inject a DLL in running process which happens to host CLR
from another application you can do that using windows hooks, but I don't
see what you can do with that afterwards , so I suppose this is not the case