private IEnumerable<IAclRule> getRulesInternal(){
     if (null == FileSystem) yield break;
     var serializer = new AclRuleXmlSerializer();
     foreach(string file in FileSystem.ResolveAll(fileName)){
         var text = FileSystem.Read(file);
         foreach (var s in serializer.Read(text)){
             s.Evidence = "local("+Path.GetFileName(Path.GetDirectoryName(file))+")";
             yield return s;
         }
     }
 }
 public void Remove(IAclRule rule){
     var olddata = FileSystem.Read(usrFileName);
     var serializer = new AclRuleXmlSerializer();
     FileSystem.Write(usrFileName, serializer.Remove(olddata, rule));
 }