title: Remove datasource binding
body: <p>I have a page like this</p>
  
  <pre><code>&lt;Page.Resources&gt;
      &lt;!--
          這個頁面顯示的群組項目集合，繫結到完整項目
          清單的子集，因為群組中的項目無法虛擬化
      --&gt;
      &lt;CollectionViewSource
          x:Name="groupedItemsViewSource"
          Source="{Binding Groups}"
          IsSourceGrouped="true"
          ItemsPath="TopItems"
          d:Source="{Binding AllGroups, Source={d:DesignInstance Type=data:SampleDataSource, IsDesignTimeCreatable=True}}"/&gt;
  
      &lt;!-- TODO: 如果已在 App.xaml 中宣告金鑰 AppName，則刪除這一行 --&gt;
      &lt;x:String x:Key="AppName"&gt;我的應用程式&lt;/x:String&gt;
  &lt;/Page.Resources&gt;
  
      &lt;local:MyGridView            
          Grid.Row="1"
          x:Name="itemGridView"
          VerticalAlignment="Top"
          Padding="116,0,40,0"
          ItemsSource="{Binding Source={StaticResource groupedItemsViewSource}}"                    
          SelectionMode="Multiple"
          IsSwipeEnabled="True"
          IsRightTapEnabled="False"
          AutomationProperties.AutomationId="ItemGridView"
          AutomationProperties.Name="Items"
          ScrollViewer.IsHorizontalScrollChainingEnabled="False"                    
          IsItemClickEnabled="True"
          ItemTemplate="{StaticResource Standard180x240ItemTemplate}"
          SelectionChanged="itemGridView_SelectionChanged_1"
          ItemClick="ItemView_ItemClick"&gt;
  
          &lt;local:MyGridView.ItemsPanel&gt;
              &lt;ItemsPanelTemplate&gt;
                  &lt;VirtualizingStackPanel Orientation="Horizontal"/&gt;
              &lt;/ItemsPanelTemplate&gt;
          &lt;/local:MyGridView.ItemsPanel&gt;
          &lt;local:MyGridView.GroupStyle&gt;
              &lt;GroupStyle&gt;
                  &lt;GroupStyle.HeaderTemplate&gt;
                      &lt;DataTemplate&gt;
                          &lt;Grid Margin="1,0,0,6" &gt;
                              &lt;Button AutomationProperties.Name="Group Title" Style="{StaticResource TextPrimaryButtonStyle}" &gt;
                                  &lt;StackPanel Orientation="Horizontal"&gt;
                                      &lt;TextBlock Text="{Binding Title}" Margin="3,-7,10,10" Style="{StaticResource GroupHeaderTextStyle}" /&gt;
                                  &lt;/StackPanel&gt;
                              &lt;/Button&gt;
                          &lt;/Grid&gt;
                      &lt;/DataTemplate&gt;
                  &lt;/GroupStyle.HeaderTemplate&gt;
                  &lt;GroupStyle.Panel&gt;
                      &lt;ItemsPanelTemplate&gt;
                          &lt;!--&lt;VariableSizedWrapGrid Orientation="Vertical" Margin="0,0,80,0"/&gt;--&gt;
                          &lt;VariableSizedWrapGrid MaximumRowsOrColumns="8" ItemWidth="180" ItemHeight="240" Orientation="Vertical" Margin="0,0,80,0"/&gt;
                      &lt;/ItemsPanelTemplate&gt;
                  &lt;/GroupStyle.Panel&gt;
              &lt;/GroupStyle&gt;
          &lt;/local:MyGridView.GroupStyle&gt;
      &lt;/local:MyGridView&gt;
  </code></pre>
  
  <p>and when i try to remove selected items in below code:</p>
  
  <pre><code>private void Delete()
  {
      var group = SampleDataSource.GetGroup("myGroup");
      foreach (SampleDataItem item in itemGridView.SelectedItems)
      {
          group.Items.Remove(item);
      }
  }
  </code></pre>
  
  <p>i get error in App.gi.cs file here</p>
  
  <pre><code> #if DEBUG &amp;&amp; !DISABLE_XAML_GENERATED_BREAK_ON_UNHANDLED_EXCEPTION
          UnhandledException += (sender, e) =&gt;
          {
              if (global::System.Diagnostics.Debugger.IsAttached)     
                  global::System.Diagnostics.Debugger.Break();
          };
   #endif
  </code></pre>
  
  <p>e.Message is shown:</p>
  
  <p>"Multiple animations in the same containing Storyboard cannot target the same property on a single element."    string</p>
  
  <p>So how can i remove selected items ?</p>
  
  <p>Thanks your help.</p>