ControlContext :: newInstance - Get property handle for initialized instance

Some actions (as insert or append) create an internal instance, which can be filled before it will be added to the collection. This instance is provided in a separate property handle. The instance can be updated by the application.

Since the instance is a transient instance, only attributes (values) might be accessed. References and relationships can be added, after storing the instance to database, only.

newInstance() returns a valid result only when being called while creating a new instance (InsertEntry, AppendEntry actions). Event handlers, which allow calling newInstance() do describe this explicitly. When being called in another context, the function throws an exception.