Using DataTrigger for TextBlock HorizontalAlignment property - wpf

Question

On my Grid I Have TextBlock and Button.
If Button is not visible I want my TextBlock.HorizontalAlignment to be set to Center.
If Button is visible I want my TextBlock.HorizontalAlignment to be set to Right. Here is my code:
<TextBlock Grid.Row="0" VerticalAlignment="Center" Name="myTextBlock" Text="{Binding TileTextId}" TextWrapping="Wrap" TextAlignment="Center" >
<TextBlock.Triggers>
<DataTrigger Binding="{Binding ElementName=myButton, Path=IsVisible}" Value="True">
<Setter Property="HorizontalAlignment" Value="Right" />
</DataTrigger>
</TextBlock.Triggers>
</TextBlock>
I get the error:
'HorizontalAlignment' member is not valid because it does not have a qualifying type name.
So I tried to add TextBlock.HorizontalAlignment, like this:
<TextBlock Grid.Row="0" VerticalAlignment="Center" Name="myTextBlock" Text="{Binding TileTextId}" TextWrapping="Wrap" TextAlignment="Center" >
<TextBlock.Triggers>
<DataTrigger Binding="{Binding ElementName=myButton, Path=IsVisible}" Value="True">
<Setter Property="TextBlock.HorizontalAlignment" Value="Right" />
</DataTrigger>
</TextBlock.Triggers>
</TextBlock>
I get the error:
XamlParseException
How should I do that?

Answer 1

Don't try to use TextBlock.Triggers, instead go for a Style with Style.Triggers.
<StackPanel>
<TextBlock Text="TextBlock Content" Margin="5">
<TextBlock.Style>
<Style TargetType="TextBlock">
<Setter Property="HorizontalAlignment" Value="Center"/>
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=myButton,Path=IsVisible}" Value="True">
<Setter Property="HorizontalAlignment" Value="Right"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
<Button x:Name="myButton" Content="Click Me!" Margin="5"/>
</StackPanel>
Take note of the documentation, as it mentions, why style triggers are needed here.
Note that the collection of triggers established on an element only
supports EventTrigger, not property triggers (Trigger). If you require
property triggers, you must place these within a style or template and
then assign that style or template to the element either directly
through the Style property, or indirectly through an implicit style
reference.

Answer 2

Try to do this with Style
<TextBlock Grid.Row="0" VerticalAlignment="Center" Name="myTextBlock" Text="{Binding TileTextId}" TextWrapping="Wrap" TextAlignment="Center" >
<TextBlock.Style>
<Style TargetType="TextBlock">
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=myButton, Path=IsVisible}" Value="True">
<Setter Property="HorizontalAlignment" Value="Right" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>