当ComboBox在DataGridComboBoxColumn中时，如何隐藏组合框的下拉列表？

<Window.Resources>
    <Style x:Key="ComboBoxStyle" TargetType="ComboBox">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ComboBox">
                    <Grid>
                        <ToggleButton x:Name="ToggleButton" ClickMode="Press" Focusable="False" IsChecked="{Binding Path=IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" />
                        <ContentPresenter x:Name="ContentPresenter" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" Content="{TemplateBinding SelectionBoxItem}" ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}" HorizontalAlignment="Left" Margin="3,3,23,3" VerticalAlignment="Center" />
                        <TextBox x:Name="PART_EditableTextBox" Background="Transparent" Focusable="False" HorizontalAlignment="Left" IsReadOnly="True" IsEnabled="{TemplateBinding IsEnabled}" Margin="3,3,23,3" Style="{x:Null}" VerticalAlignment="Center" />
                        <Popup x:Name="Popup" Focusable="False" IsOpen="{TemplateBinding IsDropDownOpen}" Placement="Bottom" PopupAnimation="Slide">
                            <Grid x:Name="DropDown" Background="White" SnapsToDevicePixels="True">
                                <ScrollViewer>
                                    <ItemsPresenter />
                                </ScrollViewer>
                            </Grid>
                        </Popup>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

<DataGridComboBoxColumn Header="ComboBox Column" SelectedItemBinding="{Binding ComboBoxProperty}" >
    <DataGridComboBoxColumn.ElementStyle>
        <Style TargetType="ComboBox">
            <Setter Property="Style" Value="{StaticResource ComboBoxStyle}" />
        </Style>
    </DataGridComboBoxColumn.ElementStyle>
    <DataGridComboBoxColumn.EditingElementStyle>
        <Style TargetType="ComboBox">
            <Setter Property="Style" Value="{StaticResource ComboBoxStyle}" />
        </Style>
    </DataGridComboBoxColumn.EditingElementStyle>
</DataGridComboBoxColumn>