chunk upload error if only one chunk c#

You can use upload sessions (a.k.a. "chunk upload") to upload small files. Using the normal upload is more efficient for small files though, since you only need to make one call as opposed to two, so I would recommend using that, despite the bit of added code complexity.

If you do want to use upload sessions to upload small files, you would need two calls:

1. `UploadSessionStartAsync`: to start the upload session and upload the data.
2. `UploadSessionFinishAsync`: to finish the upload session and commit the file. Make sure you send the correct offset.

(You can technically send the file data on either of the calls actually.)

For the error you are getting though, I'd first check what line it's occurring on. It looks like you're attempting to read from a stream, presumably one of the two `MemoryStream`s you open, when the stream is already closed. I recommend stepping through with the debugger to track down the issue.