title: WPF Binding is correct, but window does not update
body: <p>The window does not update. When it is first started, it displays the correct data. But when the data is changed, the window won't update. I made some other classes in this way and they work properly.</p>
  
  <p>The XAML class:</p>
  
  <pre><code>&lt;Window x:Class="Kwisspel.View.PlayWindow"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      xmlns:local="clr-namespace:Kwisspel.View"
      mc:Ignorable="d"
      Title="PlayWindow" Height="450" Width="800"
      DataContext="{Binding Play, Source={StaticResource Locator}}"&gt;
  &lt;Grid&gt;
      &lt;TextBlock HorizontalAlignment="Left" Margin="57,34,0,0" TextWrapping="Wrap" Text="{Binding CurrentQuestion.Text, Mode=TwoWay}" VerticalAlignment="Top" Height="43" Width="649"/&gt;
      &lt;ComboBox ItemsSource="{Binding CurrentQuestionAnswers}" SelectedItem="{Binding SelectedAnswer, Mode =TwoWay}" HorizontalAlignment="Left" Margin="230,239,0,0" VerticalAlignment="Top" Width="120"/&gt;
      &lt;Button Content="Bevestig&amp;#xD;&amp;#xA;" Command="{Binding ConfirmAnswer}" HorizontalAlignment="Left" Margin="522,270,0,0" VerticalAlignment="Top" Width="111" Height="46"/&gt;
  
  
  &lt;/Grid&gt;
  </code></pre>
  
  <p></p>
  
  <p>C# class:</p>
  
  <pre><code>public class PlayViewModel
  {
      public QuizViewModel CurrentQuiz { get; set; }
      public QuestionViewModel CurrentQuestion { get; set; }
      public QuestionViewModel[] CurrentQuizQuestions { get; set; }
      public ObservableCollection&lt;String&gt; CurrentQuestionAnswers { get; set; }
      public AnswerViewModel SelectedAnswer { get; set; }
      public ICommand ConfirmAnswer { get; set; }
      private int _Counter;
      public int CorrectAnswers { get; set; }
      public PlayWindow p;
  
   public PlayViewModel(QuizViewModel currentQuiz)
      {
          _Counter = 0;
          this.ConfirmAnswer = new RelayCommand(_ConfirmAnswer);
          this.CurrentQuiz = currentQuiz;
          this.CurrentQuizQuestions = CurrentQuiz.Questions.ToArray();
          CurrentQuestion = CurrentQuizQuestions[_Counter];
          CurrentQuestionAnswers = new ObservableCollection&lt;string&gt;(CurrentQuestion.Answers.Select(a =&gt; a.Answer.ToString()));
      }
  
      private void _ConfirmAnswer()
      {
  
          _Counter++;
          CurrentQuestion = CurrentQuizQuestions[_Counter];
          CurrentQuestionAnswers = new ObservableCollection&lt;string&gt;(CurrentQuestion.Answers.Select(a =&gt; a.Answer.ToString()));
      }
  }
  </code></pre>