it's likely this is an API break.
I don't know if we care - but I think it fits in:

❌ DISALLOWED: Changing the type of a member

The return value of a method or the type of a property or field cannot be modified. For example, the signature of a method that returns an Object cannot be changed to return a String, or vice versa.

this may cause binary compatibility issues with any code that referenced this member, can you check?

I think you are right. That was my reading of it as well. I do think we should probably make the change though. I will double check.

@mjkkirschner Yep it does fail if you directly read or set the SelectedIndex but I think we should fix this.

Hey - finally time to do this?

Marked as 3.0

Yep let's do this. Just updated the branch @mjkkirschner @QilongTang