title: Combobox with "Select All" CheckBox in SilverLight
body: <p>I've <code>ComboBox</code> where I am binding list which will appear with <code>CheckBox</code>. Now I want to add "Select All" with <code>CheckBox</code> and when user select that, remaining all <code>CheckBox</code>should get selected. Following is my code where "Select All" appears before all items but I just want it once.   </p>
  
  <p>CODE:</p>
  
  <pre><code>&lt;ComboBox x:Name="SynonymsCmbBx" ItemsSource="{Binding Synonyms}" Width="250" MaxDropDownHeight="100"  Margin="0,0,375,0"  ScrollViewer.VerticalScrollBarVisibility="Auto" Visibility="Collapsed"&gt;
      &lt;ItemsControl.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;StackPanel&gt;
                  &lt;CheckBox Content="Select All" Height="16" Name="checkBox1" IsChecked="True" FontWeight="Bold" /&gt;
                  &lt;CheckBox Content="{Binding Display}" Margin="10,0,0,0" IsChecked="{Binding Path=IsChecked, ElementName=checkBox1}" /&gt;
                  &lt;!--&lt;CheckBox Content="{Binding Display}" Margin="10,0,0,0" /&gt;--&gt;
              &lt;/StackPanel&gt;
          &lt;/DataTemplate&gt;
      &lt;/ItemsControl.ItemTemplate&gt;
  &lt;/ComboBox&gt;
  </code></pre>
  
  <p>OUTPUT:</p>
  
  <p><img src="https://i.stack.imgur.com/e6fx8.png" alt="enter image description here"></p>