title: ListBox gets only 8 items from ItemSource
body: <p>I'm developing the app on Windows phone.
  On View i have Grid with ListBox:</p>
  
  <pre><code>&lt;Grid x:Name="ContentGrid"
                Grid.Row="1"&gt;
              &lt;ListBox x:Name="TestListbox" 
                  ItemsSource="{Binding History}"                    
                  Margin="24,0"   
                  SelectionChanged="GoToSelection" 
                  ItemTemplate="{StaticResource HistoryDataTemplate}"
                  &gt;
  
              &lt;/ListBox&gt;            
          &lt;/Grid&gt;
  </code></pre>
  
  <p>History is ObservableCollection.</p>
  
  <p>And HistoryDataTemplate looks like:</p>
  
  <pre><code> &lt;phone:PhoneApplicationPage.Resources&gt;
          &lt;DataTemplate x:Key="HistoryDataTemplate"&gt;
              &lt;Grid&gt;
                  &lt;HistoryControls:HistoryItem d:LayoutOverrides="Width" Margin="0,0,0,24"/&gt;
              &lt;/Grid&gt;
          &lt;/DataTemplate&gt;
      &lt;/phone:PhoneApplicationPage.Resources&gt;
  </code></pre>
  
  <p>i use constructor of  HistoryItem for subscribing to PropertyChanged event:</p>
  
  <pre><code>     public HistoryItem()
              {
                  InitializeComponent();
                  base.Loaded+=(new RoutedEventHandler(this.HistoryControl_Loaded));
              }
   private void HistoryControl_Loaded(object sender, RoutedEventArgs e)
          {
              this._dataContext.PropertyChanged += new PropertyChangedEventHandler(this._dataContext_PropertyChanged);
          }
  </code></pre>
  
  <p>When i have 1-8 items all works correct, but for >8 items  constuctor is called only 8 times.</p>