The 'filterindex' property

Integer scalar

Valid for: OpenFile, SaveFile

The filterindex property determines which of the file extensions or types (of the list set using the filter property) is displayed in an OpenFile or SaveFile pre-defined dialog. The value is the index (in index origin 1) of the filter to display.

Usually you set filterindex before displaying the dialog. You can also read it when the dialog ends, to see whether the user has changed it. This is useful to decide the file type to use. However, under Windows and Linux, you should also check the file extension (if any), because the user can type a full filename and extension without changing the selected filter.