I want to use c ++ Mixed (c # + c ++).

I want to use c ++ Mixed (c # + c ++).
This dll works fine in the mono framework, but not in unity3d.
var oh = Activator.CreateInstance (ass.FullName, “Xbim.Geometry.XbimGeometryCreator”); << There is an error here
The alternative is to work normally
Only in Unity3d
Could someone suggest similar experiences and solutions?

Try these two manual pages:

http://www.mono-project.com/docs/advanced/pinvoke/