Apr 12 2009 · .NET Platform
This time it’s an issue with the SIZE command. As explained here,
Some servers require sending “TYPE I” before the SIZE command will work.
Note that setting FtpWebRequest.UseBinary to true (which it is by default) does not correct this. When getting the response, an exception will be thrown telling you the file is unavailable and you’ll get a 550 error with the message, “SIZE not allowed in ASCII mode”.
A discussion and Microsoft’s response to this issue is available here; it pretty much boils down to tough noogies, it’ll be fixed in a future version.