FtpWebRequest do not work well when request URI contains \r\n. This is actually handled and throws, however case when there is URL encoded %0D%0A still causes request to fail with less informative exception. It can cause issues when there is for example \r\n at the end of string as part of leftover from some parsing and such string is passed over URL encoding for safety. It would be nice to implement same check for URL encoded variant as well.