It can happen that
SftpItem.User property can be null, in case when the SFTP server does not return the user (e.g. the owner name on SFTP v4 servers and owner ID on SFTP v3 servers.)Returning it is however, not compulsory and some servers really do not do it. (as for instance our SFTP server at "test.rebex.net").
Please note that
SftpItem.User has been deprecated. Please use
SftpItem.LongName is an internal property. What exactly do you need from the property?
An alternative is to call
codeSftp.GetRawList method which returns the list of the same long names.
If you have a source code license you could make the internal property public easily.