title: how to bind an autocompletebox with a model in mvvm?
body: <p>i exposed a collection and binded it to itemsource of autocompletebox which works but selecting or changing the text on the autocompletebox doesn't update the model like a textbox or a label!</p>
  
  <p>viewmodel:</p>
  
  <pre><code>public ObservableCollection&lt;String&gt; SymptomsDb { get; private set; }
  
  private String symptom;
  
  public String Symptom
  {
      get { return symptom; }
      set
      {
          symptom = value;
          RaisePropertyChanged(() =&gt; this.Symptom);
      }
  }
  
  public AnalysisViewModel()
  {
      List&lt;String&gt; s = new List&lt;String&gt;();
      s.Add("test");
      SymptomsDb = new ObservableCollection&lt;String&gt;(s);
  }
  </code></pre>
  
  <p>view:</p>
  
  <pre><code>&lt;controls:AutoCompleteBox 
      ItemsSource="{Binding SymptomsDb}" 
      SelectedItem="{Binding Symptom}" 
      Text="{Binding Symptom}" 
      IsTextCompletionEnabled="True" 
      FilterMode="Contains"/&gt;
  </code></pre>