title: wpf IValueConverter not updating the view
body: <p>I am trying to use IValueConverter to convert the collection into proxy object for data binding.</p>
  
  <p>The converter seems to work fine, but the problem is when a new object is added or removed from the collection. The same is not refreshed in the view..</p>
  
  <p><strong>Model Object:</strong></p>
  
  <pre><code>public class A {
     public ObservableCollection&lt;string&gt; Members { get; }
  }
  </code></pre>
  
  <p><strong>Converter</strong></p>
  
  <pre><code>public class MemberConverter : IValueConverter {
      public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
          var collection = new CompositeCollection();
          var a = value as A;
  
          a.Members.ToList().ForEach(member =&gt; {
              collection.Add(new ProxyClass{ A= a, Member= member });
          });
  
          return collection; 
      }
  
      public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
          throw new System.NotImplementedException();
      }
  }
  </code></pre>
  
  <p><strong>Proxy Class</strong></p>
  
  <pre><code>public class ProxyClass {
      public A A { get; set; }
  
      public string Member{ get; set; }
   }
  </code></pre>
  
  <p><strong>XAML:</strong></p>
  
  <pre><code>&lt;DataTemplate DataType="{x:Type my:ProxyClass}"&gt;
              &lt;TextBlock Text="{Binding Path=Member}"/&gt;
  &lt;/DataTemplate&gt;
  &lt;HierarchicalDataTemplate DataType="{x:Type A}" ItemsSource="{Binding Converter={StaticResource MemberConverter}}"&gt;
              &lt;TextBlock Text ="{Binding}"/&gt;
  &lt;/HierarchicalDataTemplate&gt;
  </code></pre>