title: WinRT XAML Toolkit BindableSelections not updating UI
body: <p>Below is the xaml and c# code for handling selected items in my gridview.</p>
  
  <p>I am also using MVVM Light and everything is working, including me being able to see what's inside SelectedItems.</p>
  
  <p>However I when I attempt to clear the SelectedItems, my UI doesn't seem to update/reflect the changes made to SelectedItems.</p>
  
  <p>I am using WinRT XAML Toolkit (<a href="http://winrtxamltoolkit.codeplex.com/" rel="nofollow">http://winrtxamltoolkit.codeplex.com/</a>) which has the BindableSelection extension on a GridView</p>
  
  <p><strong>XAML</strong></p>
  
  <pre><code>&lt;controls:CustomGridView
      x:Name="VideoItemGridView"
      Grid.Row="2"
      Margin="0,-3,0,0"
      Padding="116,0,40,46"
      HorizontalContentAlignment="Stretch"
      VerticalContentAlignment="Stretch"
      IsItemClickEnabled="True"
      SelectionMode="Extended"
      Extensions:GridViewExtensions.BindableSelection="{Binding SelectedVideoItems, Mode=TwoWay}"
      ItemsSource="{Binding Source={StaticResource ViewSource}}"
      ItemTemplate="{StaticResource VideoItemTemplate}"&gt;
      &lt;GridView.ItemsPanel&gt;
          &lt;ItemsPanelTemplate&gt;
              &lt;VariableSizedWrapGrid ItemWidth="250" ItemHeight="160" /&gt;
          &lt;/ItemsPanelTemplate&gt;
      &lt;/GridView.ItemsPanel&gt;
  &lt;/controls:CustomGridView&gt;
  </code></pre>
  
  <p><strong>MyViewViewModel.cs</strong>    </p>
  
  <pre><code>#region Selected Items
  
  /// &lt;summary&gt;
  /// Gets or sets the selected video items.
  /// &lt;/summary&gt;
  public ObservableCollection&lt;object&gt; SelectedVideoItems
  {
      get { return this._selectedVideoItems; }
      set
      {
          this._selectedVideoItems = value;
          this.Set("SelectedVideoItems", ref this._selectedVideoItems, value);
      }
  }
  private ObservableCollection&lt;object&gt; _selectedVideoItems = new ObservableCollection&lt;object&gt;();
  
  #endregion
  
  #region App Bar Click Commands
  
  /// &lt;summary&gt;
  /// Gets the ClearSelection click command.
  /// &lt;/summary&gt;
  public ICommand ClearSelectionClickCommand
  {
      get
      {
          return new RelayCommand(() =&gt; this.ClearSelectionOperation());
      }
  }
  
  /// &lt;summary&gt;
  /// Selects all command operation.
  /// &lt;/summary&gt;
  private void ClearSelectionOperation()
  {
      this.SelectedVideoItems = new ObservableCollection&lt;object&gt;();
  }
  
  #endregion
  </code></pre>