You can jump to the top of file, call Get_Line(), pass the string to the DLL, go Down and repeat until Eof. DLL would buffer lines and concatenate them to one buffer. Next possibility is to mark the whole file/buffer contents as a block and send it to the clipboard. Then call the DLL which can copy it from there. But the first one is easier and more reliable. It’d be also possible to connect all lines to one string but there is well known 16 kB limitation.