If the directory is empty use rmdir from the directory above. if not use rm -r directory without a slash again from the directory above the one you want to ...
Deletes the specified directory and, if indicated, any subdirectories and files in the directory. Delete(String). Source: Directory.cs. Source: Directory.
Use the rmdir command to remove the directory, specified by the Directory parameter, from the system . The directory must be empty (it can contain only . and ..) before you can remove it, and you must have write permission in its parent directory.