Q:  Help! NXMapFile() is returning a NULL stream.  

A:  The documentation is not explicit on this point, but the file must already exist for NXMapFile() to return a valid stream.   As the name of the function indicates, it maps the file into a memory stream.  If the file doesn't exist, you can't very well map it.  If you want to open a memory stream to write to and later save to that path, you can use NXOpenMemory() to get a memory stream and then use NXSaveToFile() to write the stream out to that path.

QA760

Valid for 1.0, 2.0, 3.0