private void RemoveWord(object o)
        {
            var word = o as WordViewModel;

            if (word == null)
            {
                return;
            }

            var r = ModernDialog.ShowMessage("do you really want to remove word?", "word removing", MessageBoxButton.YesNo);

            if (r == MessageBoxResult.No)
            {
                return;
            }

            WordsService.Remove <Word>(word.WordToDisplay);

            WordsCollection.Remove(word);
        }