Provides notification of the progress of synchronous or asynchronous file management operations.

It should be inherited by classes which implement this protocol.

The enquiry functions provided by CFileBase and CFileMan may be used by the observer to display information about the progress of the operation such as error messages, the names of the target and destination files, and the number of bytes transferred during a copy operation. Notification may take place before or after an entry has been processed, or during a file copy or move. Each notification function returns a value which can be used to enable the user to control the progress of the operation, for example to cancel a long-running multiple file copy. To use this class, pass a pointer to an instance of the class to the CFileMan constructor, or use SetObserver(), defined in CFileBase.