NTFS permissions set through System.Security.AccessControl don't take

Question

I'm using System.Security.AccessControl library to add and delete NTFS permissions to files and folders (see code sample below).

    public static void addPermissions(String path, String user) {

            DirectoryInfo dInfo = new DirectoryInfo(path);
            DirectorySecurity dSecurity = dInfo.GetAccessControl();
            dSecurity.AddAccessRule(new FileSystemAccessRule(user,
                                                             FileSystemRights.FullControl,
                                                             InheritanceFlags.None,
                                                             PropagationFlags.None,
                                                             AccessControlType.Allow));
            dInfo.SetAccessControl(dSecurity);
    }

When checking properties' security tab of path in Windows Explorer, user is correctly added to the permissions list - but none of the individual permission boxes are checked - as if the FileSystemRights value was somehow "none" (which is not even a valid attribute).

Any thoughts on what I might be missing? Thank you.