public override void Execute(object parameter)
        {
            InputViewModel inputViewModel = parameter as InputViewModel;
            ObservableCollection<LetterViewModel> letterViewModelCollection = inputViewModel.LetterViewModels;
            LetterViewModel[] letterViewModels = new LetterViewModel[LIMIT];
            for(int i = 0; i < LIMIT; i++)
            {
                letterViewModels[i] = letterViewModelCollection.ElementAt(i);
            }

            WordViewModel wordViewModel = new WordViewModel(letterViewModels);
            WordViewModelManager.GetInstance().AddWord(wordViewModel);

            inputViewModel.ClearLetterViewModels();
        }
 public void AddWord(WordViewModel wordViewModel)
 {
     _wordViewModels.Add(wordViewModel);
 }