RhinoCommon API
CommonObjectEnsurePrivateCopy Method | 
            If you want to keep a copy of this class around by holding onto it in a variable after a command
            completes, call EnsurePrivateCopy to make sure that this class is not tied to the document. You can
            call this function as many times as you want.
            
Namespace: Rhino.Runtime
Assembly: RhinoCommon (in RhinoCommon.dll)