public CompositeUnDoCommand(CommandUndo command)
     : this(new CommandUndo[] { command }) { }
 /// <summary>
 /// Adds a SubCommand at the end of the composite command flow
 /// </summary>
 /// <param name="command"></param>
 public void Add(CommandUndo command) {
     _commands.Add(command);
 }
 public UnDoCommandViewModel(CommandUndo command) {
     _command = command;
 }