Here I share a simple example for exporting data in ASCII ‘csv’ file format. The file is saved to the folder that is set up in the web browser.

    public static void main(Args _args)
    {
       Filename fileName = 'Filename.Txt';
        AsciiStreamIo asciiIo = AsciiStreamIo::constructForWrite();

        asciiIo.outRecordDelimiter("\r\n");
        asciiIo.outFieldDelimiter(";");

        asciiIo.write('Line 1');
        asciiIo.write('Line 2');
        File::SendFileToUser(asciiIo.getStream(),'asciiFile.txt');
    }

Here is another example code. This one is reading / importing data in ASCII ‘csv’ file format. The csv file can be selected by the user from his or her local disk.

public static void main(Args _args)
{
    FileUploadTemporaryStorageResult    uploadFileResult = File::GetFileFromUser();
    System.IO.Stream                    readStream = File::UseFileFromURL(uploadFileResult.getDownloadUrl());
    AsciiStreamIo                       inFile = AsciiStreamIo::constructForRead(readStream);

    container               readCon;
    str                     recordRead;
    int                     nRead;

    inFile.inFieldDelimiter("\r\n");
    inFile.inRecordDelimiter("\r\n");

    if (!inFile)
    {
        //FileName = uploadFileResult.getFileName();
        Error('Cannot open file. Import failed.');
    }
    else
    {
        readCon = inFile.read();
        while (inFile.status() == IO_Status::OK)
        {
            recordRead = conPeek(readCon, 1);
            info(recordRead);
            readCon = inFile.read();
            nRead++;
        }
    }
}

You can paste these codes to a runnable class and it will work or copy from https://github.com/PeterProkopecz/AX/tree/master/D365FO_FileReadWrite. You can customize them to fit your needs. Use ‘TextStreamIo’ class instead of ‘AsciiStreamIo’ in case you want to use normal text files.