Это зависит от ListPicker.ExpansionMode
. Если это ExpansionAllowed
- ваш стиль должен выглядеть примерно так:
<Style TargetType="toolkit:ListPickerItem">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="Padding" Value="8 6"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="toolkit:ListPickerItem">
<Grid x:Name="grid" Background="{TemplateBinding Background}">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected">
<Storyboard>
<ObjectAnimationUsingKeyFrames
Storyboard.TargetName="ContentContainer"
Storyboard.TargetProperty="Foreground"
Duration="0">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<!-- Normal color -->
<SolidColorBrush Color="Black"/>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Selected">
<Storyboard>
<ObjectAnimationUsingKeyFrames
Storyboard.TargetName="ContentContainer"
Storyboard.TargetProperty="Foreground"
Duration="0">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<!-- Selected color -->
<SolidColorBrush Color="Orange"/>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<!-- Optionally - background selected color -->
<!--<ObjectAnimationUsingKeyFrames
Storyboard.TargetName="grid"
Storyboard.TargetProperty="Background"
Duration="0">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<SolidColorBrush Color="Gray"/>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>-->
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<ContentControl
x:Name="ContentContainer"
Content="{TemplateBinding Content}"
ContentTemplate="{TemplateBinding ContentTemplate}"
Foreground="{TemplateBinding Foreground}"
VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
Margin="{TemplateBinding Padding}" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Однако, если это FullScreenOnly
- единственный способ - изменить исходный код инструментария и собрать его с необходимыми изменениями. На мой взгляд, оно того не стоит.