private void SaveCommands()
        {
            if (_historyStorage == null)
            {
                return;
            }

            try
            {
                string[] commands = null;
                lock (_commandsWriteLock)
                {
                    commands = _commands.ToArray();
                }
                lock (_historyStorage)
                {
                    _historyStorage.Save(commands);
                }
            }
            catch
            {
                // ignore
            }
        }