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?
– Dale
There are a couple of samples in the Developer Samples Repo on GitHub that might help you.
Let me know if either of these helps.
– Dale