Selecting parts of a block geometry doesn’t work the same as regular geometries. I end up with a reference to the InstanceObject and the component index doesn’t make any sense to me (e.g. 2147483635). How to extract a curve from such an object without calling explode before?
What language are you coding in (e.g. Python, C#, C++)?
Are you inside Rhino?
I’m using C#.