获取控件值,该如何解决

  <sdk:DataGridTemplateColumn Header="全选"  CanUserResize="False" Width="44">
                            <sdk:DataGridTemplateColumn.HeaderStyle>
                                <Style TargetType="sdk:DataGridColumnHeader">
                                    <Setter Property="HorizontalContentAlignment" Value="Center"></Setter>
                                    <Setter Property="VerticalContentAlignment" Value="Center"></Setter>
                                    <Setter Property="ContentTemplate">
                                        <Setter.Value>
                                            <DataTemplate>
                                                <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
                                                    <TextBlock Text="" Width="12"/>
                                                    <CheckBox Name="chkAll" Checked="chkAll_Checked" Unchecked="chkAll_Unchecked"  />
                                                </StackPanel>
                                            </DataTemplate>
                                        </Setter.Value>