Hi,
in a sample app (Folderitem Dialogs), I see the follow code:
// The filter is what type of file you are looking for
// The filters are defined in the File Types dialog
// inside the edit menu
dialog.Filter = text/plain
In my edit menu (xojo 2016R4.1) there is not “File Type” inside edit menu.
To add a FileType, go to the Insert Menu (MenuBar) and… Insert a FileType (or something that looks like that).
Then, in the Navigation pane (left), setach for FileType1,
select it,
rename it to something meaningful (that’s for you)
then add a File Type (look in the middle of the window since I forget that one),
then you have PopupMenus to add either a blank you have to populate or at the window bottom to choose some already defined.
“text/plain” is in the PopupMenu.