public QuestionListViewModel(IList<Question> models)
 {
     Model = models;
     Questions = new ObservableCollection<QuestionViewModel>();
     foreach(Question q in Model)
     {
         QuestionViewModel qvm = new QuestionViewModel(q);
         Questions.Add(qvm);
         qvm.PropertyChanged += qvm_PropertyChanged;
     }
 }
 void qvm_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
 {
     if (e.PropertyName.Equals("Category"))
         Selected = sender as QuestionViewModel;
 }
 private void AddQuestion_Command(object param)
 {
     Question q = new Question();
     q.QuestionText = "Neue Frage";
     QuestionViewModel sel = param as QuestionViewModel;
     if (sel != null)
         q.Category = sel.Category;
     Model.Add(q);
     QuestionViewModel qvm = new QuestionViewModel(q);
     qvm.PropertyChanged += qvm_PropertyChanged;
     Questions.Add(qvm);
     App.SaveQuestionsAsync();
 }