WPF Style DataTrigger with binding to DataContext not working

Question

I have a TextBox with a style that has a DataTrigger which changes the text, like this:

Answer 1

Dependency Properties can be set from many different places; inline, animations, coercion, triggers, etc. As such a Dependency Property Value Precedence list was created and this dictates which changes override which other changes. Because of this order of precedence, we can't use a Trigger to update a property that is explicitly set inline in your XAML. Try this instead:

<Grid>
    <TextBlock>
        <TextBlock.Style>
            <Style BasedOn="{StaticResource TextStyle}" TargetType="TextBlock">
                <!-- define your default value here -->
                <Setter Property="Text" Value="Foo" />
                <Style.Triggers>
                    <DataTrigger Binding="{Binding MyBool}" Value="True">
                        <!-- define your triggered value here -->
                        <Setter Property="Text" Value="Bar" />
                    </DataTrigger>
                 </Style.Triggers>
             </Style>
         </TextBlock.Style>
     </TextBlock>
</Grid>