public void ChangeViewModel(INamedViewModel newViewModel)
        {
            // verify if view model exists
            if (!_viewModels.Contains(newViewModel))
            {
                throw new ArgumentOutOfRangeException();
            }

            _currentViewModel = newViewModel;
        }
 public ApplicationViewModel(IEnumerable <INamedViewModel> viewModels)
 {
     _viewModels       = viewModels;
     _currentViewModel = _viewModels.FirstOrDefault();
 }