Hello everyone
When I use the GetSelectedObjects() method, I found that the order of this method is frame selection from the bottom left corner to the top.like this.
I found a solution: first create a dictionary, and then subscribe to three events (Rhino.RhinoDoc.SelectObjects/Rhino.RhinoDoc.DeselectObjects/Rhino.RhinoDoc.DeselectAllObjects) to record the order of selection.