Определите стиль для PhoneTextBox в Windows Phone

Я переписываю стиль для PhoneTextBox, изменяя фон по умолчанию на «прозрачный», передний план на «белый» и BorderBrush на «белый», потому что я хочу создать темную тему.

Но возникла проблема, пропал индикатор ввода текста. Я благодарю, причина в том, что передний план индикатора ввода текста черный, поэтому пользователь его не видит. Но я не могу найти способ определить передний план индикатора ввода текста. Любые советы будут appricated.

PS. Я не знаю, как описать индикатор, поэтому я придумываю слово «индикатор ввода текста», которое показано ниже:

Нормальная ситуация, появляется черная вертикальная линия.

После перезаписи стиля пользователь не видит черную вертикальную линию:

и xaml-код:

 <Style x:Key="PhoneTextBoxStyle" TargetType="toolkit:PhoneTextBox">
        <Setter Property="FontFamily" Value="{StaticResource PhoneFontFamilyNormal}"/>
        <Setter Property="FontSize" Value="{StaticResource PhoneFontSizeMediumLarge}"/>
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="Foreground" Value="White"/>
        <Setter Property="BorderBrush" Value="White"/>
        <Setter Property="SelectionBackground" Value="{StaticResource PhoneAccentBrush}"/>
        <Setter Property="SelectionForeground" Value="White"/>
        <Setter Property="BorderThickness" Value="2"/>
        <Setter Property="Padding" Value="{StaticResource PhoneBorderThickness}"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="toolkit:PhoneTextBox">
                    <Grid x:Name="RootGrid" Background="Transparent">
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Disabled">
                                </VisualState>
                                <VisualState x:Name="Enabled">
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="FocusStates">
                                <VisualState x:Name="Focused">
                                </VisualState>
                                <VisualState x:Name="Unfocused"/>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="LengthIndicatorStates">
                                <VisualState x:Name="LengthIndicatorVisible">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="LengthIndicator">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Visible</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Margin" Storyboard.TargetName="RootGrid">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0" Value="0, 0, 0, 27"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Opacity" Storyboard.TargetName="LengthIndicator">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0" Value="0.6"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <DoubleAnimation Duration="0:0:0.350" To="32" Storyboard.TargetProperty="(UIElement.RenderTransform).(TranslateTransform.Y)" Storyboard.TargetName="LengthIndicator">
                                            <DoubleAnimation.EasingFunction>
                                                <ExponentialEase Exponent="6"/>
                                            </DoubleAnimation.EasingFunction>
                                        </DoubleAnimation>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="LengthIndicatorHidden">
                                    <Storyboard>
                                        <DoubleAnimation Duration="0:0:0.350" To="0" Storyboard.TargetProperty="(UIElement.RenderTransform).(TranslateTransform.Y)" Storyboard.TargetName="LengthIndicator">
                                            <DoubleAnimation.EasingFunction>
                                                <ExponentialEase Exponent="6"/>
                                            </DoubleAnimation.EasingFunction>
                                        </DoubleAnimation>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Margin" Storyboard.TargetName="RootGrid">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0" Value="0, 0, 0, 0"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Opacity" Storyboard.TargetName="LengthIndicator">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0.350" Value="0"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="LengthIndicator">
                                            <DiscreteObjectKeyFrame KeyTime="0:0:0.350">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Collapsed</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Border x:Name="LengthIndicatorBorder">
                            <TextBlock x:Name="LengthIndicator" Foreground="{StaticResource PhoneContrastBackgroundBrush}" FontSize="{StaticResource PhoneFontSizeNormal}" HorizontalAlignment="Right" Margin="0" Opacity="0" TextAlignment="Right" VerticalAlignment="Bottom">
                                    <TextBlock.RenderTransform>
                                        <TranslateTransform/>
                                    </TextBlock.RenderTransform>
                            </TextBlock>
                        </Border>
                        <Border x:Name="HintBorder" BorderBrush="{TemplateBinding BorderBrush}" 
                                BorderThickness="{TemplateBinding BorderThickness}" 
                                Background="{TemplateBinding Background}" Margin="0">
                            <Grid>
                                <ContentControl x:Name="HintContent" Background="Transparent" Content="{TemplateBinding Hint}"
                                                HorizontalAlignment="Left" Margin="3,5,3,0" Style="{TemplateBinding HintStyle}" 
                                                Foreground="Gray"
                                                Visibility="{TemplateBinding ActualHintVisibility}" VerticalAlignment="Top"/>
                                <ContentControl x:Name="ContentElement" BorderThickness="0" HorizontalContentAlignment="Stretch" 
                                                Margin="{StaticResource PhoneTextBoxInnerMargin}" 
                                                Padding="{TemplateBinding Padding}"
                                                VerticalContentAlignment="Stretch"/>
                            </Grid>
                        </Border>
                        <Border x:Name="TextBorder" BorderBrush="White" 
                                BorderThickness="{TemplateBinding BorderThickness}" 
                                Background="Transparent" Margin="0" Visibility="Collapsed">
                            <TextBox x:Name="Text" Foreground="White" 
                                     FontWeight="{TemplateBinding FontWeight}" FontStyle="{TemplateBinding FontStyle}" 
                                     FontSize="{TemplateBinding FontSize}" FontFamily="{TemplateBinding FontFamily}"
                                     HorizontalAlignment="Left" SelectionForeground="{TemplateBinding SelectionForeground}" 
                                     SelectionBackground="{TemplateBinding SelectionBackground}" 
                                     TextAlignment="{TemplateBinding TextAlignment}" TextWrapping="{TemplateBinding TextWrapping}" 
                                     Text="{TemplateBinding Text}"/>
                        </Border>
                        <Border x:Name="ActionIconBorder" Background="Transparent" HorizontalAlignment="Right" Height="54" VerticalAlignment="Bottom" Width="54">
                            <Image x:Name="ActionIcon" Height="54" Source="{TemplateBinding ActionIcon}" Width="54"/>
                        </Border>
                        <TextBlock x:Name="MeasurementTextBlock" FontWeight="{TemplateBinding FontWeight}" FontStyle="{TemplateBinding FontStyle}" FontStretch="{TemplateBinding FontStretch}" FontSize="{TemplateBinding FontSize}" FontFamily="{TemplateBinding FontFamily}" IsHitTestVisible="False" Margin="8" Opacity="0" TextAlignment="{TemplateBinding TextAlignment}" TextWrapping="{TemplateBinding TextWrapping}" Text="{TemplateBinding Text}"/>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>