I have gotten a checkbox to show up inside a column header. How can I get access to the checkbox programmatically? My column definition is below:

<ig:CheckBoxColumn IsReadOnly="False" AddNewRowEditorTemplateHorizontalContentAlignment="Center" AddNewRowEditorTemplateVerticalContentAlignment="Center" AddNewRowItemTemplateHorizontalContentAlignment="Center" AddNewRowItemTemplateVerticalContentAlignment="Center" AllowCaseSensitiveSort="True" EditorHorizontalContentAlignment="Center" EditorVerticalContentAlignment="Center" FixedIndicatorDirection="{x:Null}" HeaderTextHorizontalAlignment="Center" HorizontalContentAlignment="Center" IsFilterable="True" IsFixable="True" IsGroupable="True" IsHideable="True" IsMovable="True" IsResizable="True" IsSortable="True" IsSummable="False" Key="Suppress" VerticalContentAlignment="Center" IsFixed="Left">
  <ig:CheckBoxColumn.HeaderTemplate>
    <DataTemplate x:Name="SelectAllHeader">
      <CheckBox x:Name="CheckAll" HorizontalAlignment="Center" IsChecked="{Binding SelectAll.AllItemsChecked, Mode=OneWay}" Checked="All_Checked" Unchecked="All_Checked">
      </CheckBox>
    </DataTemplate>
  </ig:CheckBoxColumn.HeaderTemplate>
  <ig:CheckBoxColumn.FilterColumnSettings>
    <ig:FilterColumnSettings FilterCaseSensitive="False" FilterCellValue="{x:Null}" FilterMenuClearFiltersString="{x:Null}" FilterMenuTypeSpecificFiltersString="{x:Null}" FilteringOperand="{x:Null}" />
  </ig:CheckBoxColumn.FilterColumnSettings>
  <ig:CheckBoxColumn.SummaryColumnSettings>
    <ig:SummaryColumnSettings />
  </ig:CheckBoxColumn.SummaryColumnSettings>
</ig:CheckBoxColumn>