Indeed the square bracket [ has a special meaning in the file mask:
https://winscp.net/eng/docs/file_mask#basic

In scripting you have to escape it like:
rm -- "/C:/Shares/Temp/[[]2015] Test"

In .NET assembly, you can (should) use RemotePath.EscapeFileMask method:
https://winscp.net/eng/docs/library_remotepath_escapefilemask

Issue seems to be related to directories that start with '['. If I remove that the remove works. Log attached.

mmedic wrote:

I have tried using Session.RemoveFiles with and without a trailing slash but without success. Operation succeeds but the RemovalOptionResult shows 0 removals. I have verified that the directory exists on the remote server. It does contain [] (brackets) in the name. I am not sure if that causes any issues.

Please attach a full session log file showing the problem (using the latest version of WinSCP).

I assume you meant to say "Session.RemoveFiles should not remove the directory with [at least one] file [in it]." My directory is indeed empty but once the command is executed it reports that there was no match found.

In any event, how does not remove a directory (empty or not)? I downloaded the source code and created a method RemoveDirectory which calls and that works but the original library does not seem to provide this functionality. I am missing something?

Session.RemoveFiles should not remove the directory with the last file.

May you find solution here:
https://winscp.net/eng/docs/library_session_removefiles

I have tried using Session.RemoveFiles with and without a trailing slash but without success. Operation succeeds but the RemovalOptionResult shows 0 removals. I have verified that the directory exists on the remote server. It does contain [] (brackets) in the name. I am not sure if that causes any issues.