How to align Text in DataTemplate choosen by a DataTemplateSelector?

Question

I am trying to align text in a DataTemplate of a ListBox depending on the choice of the DataTemplateSelector.

What I want is something like this:

And tried to use a DataTemplateSelector

    <DataTemplate x:Key="RequestTemplate" DataType="local:Message">
            <TextBlock Text="{Binding Text}" Background="LightGreen" TextAlignment="Left" TextWrapping="Wrap"/>
    </DataTemplate>

    <DataTemplate x:Key="ResponseTemplate" DataType="local:Message" >
            <TextBlock Text="{Binding Text}"  Background="Yellow" TextAlignment="Right" TextWrapping="Wrap"/>
    </DataTemplate>

    <local:MesssageDataTemplateSelector x:Key="MessageDataTemplateSelector"
          ResponseTemplate="{StaticResource ResponseTemplate}"
          RequestTemplate="{StaticResource RequestTemplate}" />

The ListBox itself:

<ListBox ItemTemplateSelector="{StaticResource MessageDataTemplateSelector}"  ItemsSource="{Binding Messages}" />

The colors are applied the alignment is not.

I also tried HorizontalAlignment, also not working. How to accomplish the effect?

Answer 1

One solution is to change the ListBoxItem style so that its HorizontalContentAlignment is Stretch:

<ListBox.ItemContainerStyle>
    <Style TargetType="ListBoxItem">
        <Setter Property="HorizontalContentAlignment" Value="Stretch" />
    </Style>
</ListBox.ItemContainerStyle>