Question

I am trying to make a style that only gets applied if the parent element of the element that the style refers to, has another specific style. Kind of like in CSS where you can do “.class1 .class2” to specify that the “class2” theme only applies if it is within an element with the class “class1”.

I do not wish to use any form of external DLLs or libraries for this task. I want to know if it’s possible to implement on my own.

I’ve tried using MultiTriggers with no luck.

I have a style that applies to all TextBlocks. I want the textblock to do the following:

If the font-size of the textblock is 11 and the parent element’s style is “PinnedSuggestion”, set the foreground color to “#FF505050”.

If the font-size of the textblock is 11 and the parent element’s style is “Suggestion”, set the foreground color to “#FFCCCCCC”.

The conditions that I have tried to write to make this work, are as follows (the font-size condition is true, but the other one is not). The conditions are inside a style that applies to all textblocks in general.

                <MultiDataTrigger>
                    <MultiDataTrigger.Conditions>
                        <Condition Binding="{Binding RelativeSource={RelativeSource Self}, Path=FontSize}" Value="11" />
                        <Condition Binding="{Binding RelativeSource={RelativeSource Self}, Path=Style}" Value="{StaticResource PinnedSuggestion}" />
                    </MultiDataTrigger.Conditions>
                    <Setter Property="Foreground" Value="#FFFF5050"></Setter>
                </MultiDataTrigger>

I am not sure what I am doing wrong in this case. Below you see my ListBoxItem style for the “Suggestion” style. The PinnedSuggestion looks exactly the same (except for a few minor changes).

<Style x:Key="Suggestion" TargetType="{x:Type ListBoxItem}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="ListBoxItem">
                <Grid Name="Container" Margin="0,0,0,0">
                    <Rectangle Margin="0,2,0,2" Stroke="Black" Name="Background" SnapsToDevicePixels="True" RadiusX="7" RadiusY="7" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                    <Rectangle Margin="2,4,2,4" Name="BackgroundTwo" StrokeThickness="3"  SnapsToDevicePixels="True" RadiusX="3" RadiusY="3" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                    <ContentPresenter Margin="0"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

The contentpresenter of that ListBoxItem style is what contains the textblocks that I want this technique to work with.

So, to summarize…

A ListBoxItem with the style “Suggestion” applied will have a TextBlock in it. The TextBlock style (due to its target type) will automatically apply to that, and I want the multitrigger conditions described above to work as they should.

My situation is kind of hard to explain. I explained everything as well as I could.

Answer 1

The parent element whose style you want to inspect is not the direct parent of the TextBlock; it could be arbitrarily higher in the visual tree. So your second condition needs to look for an ancestor of a particular type like this:

<Condition Binding="{Binding RelativeSource={RelativeSource AncestorType=ListBoxItem}, Path=Style}" Value="{StaticResource Suggestion}" />

Here is a complete working example, tested with .NET4:

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Window.Resources>
    <Style x:Key="Suggestion" TargetType="{x:Type ListBoxItem}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ListBoxItem">
                    <Grid Name="Container" Margin="0,0,0,0">
                        <Rectangle Margin="0,2,0,2" Stroke="Blue" Name="Background" SnapsToDevicePixels="True" RadiusX="7" RadiusY="7" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                        <Rectangle Margin="2,4,2,4" Name="BackgroundTwo" StrokeThickness="3"  SnapsToDevicePixels="True" RadiusX="3" RadiusY="3" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                        <ContentPresenter Margin="0"/>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style x:Key="PinnedSuggestion" TargetType="{x:Type ListBoxItem}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ListBoxItem">
                    <Grid Name="Container" Margin="0,0,0,0">
                        <Rectangle Margin="0,2,0,2" Stroke="Green" Name="Background" SnapsToDevicePixels="True" RadiusX="7" RadiusY="7" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                        <Rectangle Margin="2,4,2,4" Name="BackgroundTwo" StrokeThickness="3"  SnapsToDevicePixels="True" RadiusX="3" RadiusY="3" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                        <ContentPresenter Margin="0"/>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style x:Key="Neutral" TargetType="{x:Type ListBoxItem}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ListBoxItem">
                    <Grid Name="Container" Margin="0,0,0,0">
                        <Rectangle Margin="0,2,0,2" Stroke="Black" Name="Background" SnapsToDevicePixels="True" RadiusX="7" RadiusY="7" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                        <Rectangle Margin="2,4,2,4" Name="BackgroundTwo" StrokeThickness="3"  SnapsToDevicePixels="True" RadiusX="3" RadiusY="3" Width="Auto" Height="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"></Rectangle>
                        <ContentPresenter Margin="0"/>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style TargetType="{x:Type TextBlock}">
        <Style.Triggers>
            <MultiDataTrigger>
                <MultiDataTrigger.Conditions>
                    <Condition Binding="{Binding RelativeSource={RelativeSource Self}, Path=FontSize}" Value="11" />
                    <Condition Binding="{Binding RelativeSource={RelativeSource AncestorType=ListBoxItem}, Path=Style}" Value="{StaticResource Suggestion}" />
                </MultiDataTrigger.Conditions>
                <Setter Property="Foreground" Value="Red"></Setter>
            </MultiDataTrigger>
            <MultiDataTrigger>
                <MultiDataTrigger.Conditions>
                    <Condition Binding="{Binding RelativeSource={RelativeSource Self}, Path=FontSize}" Value="11" />
                    <Condition Binding="{Binding RelativeSource={RelativeSource AncestorType=ListBoxItem}, Path=Style}" Value="{StaticResource PinnedSuggestion}" />
                </MultiDataTrigger.Conditions>
                <Setter Property="Foreground" Value="Yellow"></Setter>
            </MultiDataTrigger>
        </Style.Triggers>
    </Style>
</Window.Resources>
<Grid>
    <ListBox>
        <ListBoxItem Style="{StaticResource Neutral}">
            <TextBlock FontSize="10" Text="Style=Neutral, FontSize=10"/>
        </ListBoxItem>
        <ListBoxItem Style="{StaticResource Neutral}">
            <TextBlock FontSize="11" Text="Style=Neutral, FontSize=11"/>
        </ListBoxItem>
        <ListBoxItem Style="{StaticResource Suggestion}">
            <TextBlock FontSize="10" Text="Style=Suggestion, FontSize=10"/>
        </ListBoxItem>
        <ListBoxItem Style="{StaticResource Suggestion}">
            <TextBlock FontSize="11" Text="Style=Suggestion, FontSize=11"/>
        </ListBoxItem>
        <ListBoxItem Style="{StaticResource PinnedSuggestion}">
            <TextBlock FontSize="10" Text="Style=PinnedSuggestion, FontSize=10"/>
        </ListBoxItem>
        <ListBoxItem Style="{StaticResource PinnedSuggestion}">
            <TextBlock FontSize="11" Text="Style=PinnedSuggestion, FontSize=11"/>
        </ListBoxItem>
    </ListBox>
</Grid>