Debug or fix c# drive api code to export slide presentation to ppt

It just needs a fix

var stream = new System.IO.MemoryStream();
var request = DriversService.Files.Export(presentationId, "application/vnd.openxmlformats-officedocument.presentationml.presentation").DownloadWithStatus(stream);
var fileInfo = new FileInfo("output.pptx");
using (var streamWrite = fileInfo.Open(FileMode.Create, FileAccess.Write))
stream.CopyTo(streamWrite);

This always leads me to a 0bytes file being written, even though the stream download completes and is 33kb its not writing the file.

$30 - no more - should be 10/20 mins work.