Ответ 1
Я не переставал понимать всю проблему, но если вы не хотите, чтобы содержимое ListBoxItem было точно таким же, как ItemTemplate, замените ContentControl на ContentPresenter.
<ControlTemplate>
<Grid>
<Rectangle x:Name="fillColor" Fill="#d2c2f9" IsHitTestVisible="False" RadiusY="1" RadiusX="1" Margin="0,3" Opacity="0"/>
<Rectangle x:Name="fillColor2" Fill="#d2c2f9" IsHitTestVisible="False" RadiusY="1" RadiusX="1" Margin="0,3" Opacity="0"/>
<Rectangle x:Name="FocusVisualElement" RadiusY="1" RadiusX="1" StrokeThickness="1" Visibility="Collapsed" Margin="0,3"/>
<ContentPresenter />
</Grid>
<Grid>
<Border BorderBrush="#d2c2f9" BorderThickness="1">
<ContentPresenter />
</Border>
<Rectangle x:Name="FocusVisualElement" RadiusY="1" RadiusX="1" StrokeThickness="1" Visibility="Collapsed" Margin="0,3"/>
</Grid>
отредактируйте 2: удалите itemtemplate, установите фон списка с привязкой Setter к вашему конвертеру, а в вашем шаблоне ваша Grid Backgorund привязана к шаблону родительского фона.
<Style x:Key="ListBoxItemStyle" TargetType="ListBoxItem">
<!-- this -->
<Setter Property="Background" Value="{Binding Path=Content,Converter={StaticResource AnswerCellBackgroundConvertor}}"/>
<Setter Property="BorderThickness" Value="0"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="Padding" Value="0"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ListBoxItem">
<!-- and this Background-->
<Grid x:Name="LayoutRoot"
Background="{TemplateBinding Background}"
HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver">
<Storyboard>
<DoubleAnimation Duration="0" To=".75" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="fillColor"/>
</Storyboard>
</VisualState>
<VisualState x:Name="MouseLeave">
<Storyboard>
<DoubleAnimation Duration="0" To="0.75" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="contentPresenter"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Disabled">
<Storyboard>
<DoubleAnimation Duration="0" To=".55" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="contentPresenter"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected"/>
<VisualState x:Name="Selected">
<Storyboard>
<DoubleAnimation Duration="0" To=".75" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="fillColor2"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="FocusVisualElement">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Unfocused"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<ContnerPresenter />
<Rectangle x:Name="fillColor" Fill="#d2c2f9" IsHitTestVisible="False" RadiusY="1" RadiusX="1" Margin="0,3" Opacity="0"/>
<Rectangle x:Name="fillColor2" Fill="#d2c2f9" IsHitTestVisible="False" RadiusY="1" RadiusX="1" Margin="0,3" Opacity="0"/>
<Rectangle x:Name="FocusVisualElement" RadiusY="1" RadiusX="1" StrokeThickness="1" Visibility="Collapsed" Margin="0,3"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>