title: Setting Itemsource for ControlTemplate
body: <p>I have created an AutocompleteBox and it works completely fine outside a ControlTemplate. When I place it within a Control template, the autocompletebox is no longer populated with any items. </p>
  
  <pre><code>&lt;ControlTemplate x:Key="EditAppointmentTemplate" TargetType="telerik:SchedulerDialog"&gt;
      &lt;Grid Margin="6"&gt;
          &lt;Grid.ColumnDefinitions&gt;
              &lt;ColumnDefinition Width="97" /&gt;
              &lt;ColumnDefinition Width="*" /&gt;
          &lt;/Grid.ColumnDefinitions&gt;
          &lt;TextBlock Text="Participants" Margin="6 0" VerticalAlignment="Center" HorizontalAlignment="Left" /&gt;
          &lt;telerik:RadAutoCompleteBox Margin="6 0"
                                      Grid.Column="1"
                                      ItemsSource="{Binding Atts}" 
                                      SelectedItems="{Binding SelectedAttendees,Mode=TwoWay}" 
                                      DisplayMemberPath="DisplayName" 
                                      TextSearchPath="Search" 
                                      Style="{StaticResource MultiAutoBox}" 
                                      WatermarkContent="Search ..." 
                                      MinHeight="55" VerticalContentAlignment="Top" Padding="5"&gt;
          &lt;/telerik:RadAutoCompleteBox&gt;
      &lt;/Grid&gt;
  &lt;/ControlTemplate&gt;
  
  &lt;Style x:Key="EditAppointmentDialogStyle" TargetType="telerik:SchedulerDialog"&gt;
       ....
       &lt;Setter Property="Template" Value="{StaticResource EditAppointmentTemplate}" /&gt;
       ....
  &lt;Style x:Key="EditAppointmentDialogStyle"/&gt;
  
  &lt;telerik:RadScheduleView x:Name="scheduleview" ....
                           EditAppointmentDialogStyle="{StaticResource EditAppointmentDialogStyle}"
                           ....
   &lt;telerik:RadScheduleView x:Name="scheduleview"/&gt;
  </code></pre>
  
  <p>I'm thinking I have to set the ItemsSource to target a relative ancestor
  I tried the following and the itemsource isn't populating still.</p>
  
  <pre><code>ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type telerik:SchedulerDialog}}, Path=Atts}"
  </code></pre>