isOpen(): Boolean;
The isOpen method of the File class returns true if the associated physical file is open by the current process. It does not return true if the file has been opened by another process.
Use the File class tryOpen method to determine if the file is in use by another process.
The code fragment in the following example shows the use of the isOpen method.
if not app.isValidObject(file) then
create file transient;
elseif file.isOpen then
file.close;
endif;