3ds Max provides a container manager object, represented by the class IContainerManager for working with containers. A pointer to the container manager object can be retrieved using the GetContainerManagerInterface() global function.
Individual containers are exposed by 3ds Max using the IContainerObject interface. A container is represented in the scene as a box, and has an INode dedicated to it. This allows the user to select a container.
The container manager object can be used to retrieve an IContainerObject associated with an INode as follows:
bool IsContainer(INode* node) { IContainerObject* co = GetContainerManagerInterface()->IsContainerNode( node); return co != NULL; }