Applying Style to child elements in Silverlight 4 - silverlight

Question

In Silverlight 4 (using Expression Blend 4), how can I alter the Font size of a TextBox within the style of the Border containing it? I'm converting the style from WPF to Silverlight (fun always). Here is what I have:
<Style x:Key="Title" TargetType="Border">
<Setter Property="TextBlock.VerticalAlignment" Value="Center"/>
<Setter Property="TextBlock.TextAlignment" Value="Center"/>
<Setter Property="TextBlock.FontSize" Value="48"/>
<Setter Property="TextBlock.Foreground" Value="{StaticResource TextForeground}"/>
<Setter Property="VerticalAlignment" Value="Top"/>
<Setter Property="HorizontalAlignment" Value="Stretch"/>
<Setter Property="Background" Value="{StaticResource TitleBackground}"/>
<Setter Property="Padding" Value="25,0"/>
</Style>
It is not working. It gives me the following exception in the designer:
Edits:
Ok, I know this is possible in WPF. Is it simply not possible in Silverlight (without taking on a whole theme construct as Xin suggests?)

Answer 1

Actually you might be able to get what you want from silverlight toolkit themes. You can find it here (Theming -> Theme Browser).
Update:
First you need to create a class that inherits from the Theme (System.Windows.Controls.Theming). I basically copied from the source code and renamed it.
/// <summary>
/// Implicitly applies the border theme to all of its descendent
/// FrameworkElements.
/// </summary>
/// <QualityBand>Preview</QualityBand>
public class BorderTheme : Theme
{
/// <summary>
/// Stores a reference to a Uri referring to the theme resource for the class.
/// </summary>
private static Uri ThemeResourceUri = new Uri("/theming;component/Theme.xaml", UriKind.Relative);
/// <summary>
/// Initializes a new instance of the ExpressionDarkTheme class.
/// </summary>
public BorderTheme()
: base(ThemeResourceUri)
{
var a = ThemeResourceUri;
}
/// <summary>
/// Gets a value indicating whether this theme is the application theme.
/// </summary>
/// <param name="app">Application instance.</param>
/// <returns>True if this theme is the application theme.</returns>
public static bool GetIsApplicationTheme(Application app)
{
return GetApplicationThemeUri(app) == ThemeResourceUri;
}
/// <summary>
/// Sets a value indicating whether this theme is the application theme.
/// </summary>
/// <param name="app">Application instance.</param>
/// <param name="value">True if this theme should be the application theme.</param>
public static void SetIsApplicationTheme(Application app, bool value)
{
SetApplicationThemeUri(app, ThemeResourceUri);
}
}
Then you just need to create a resource dictionary and name it Theme.xaml, and put all your styles inside.
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Style TargetType="Border">
<Setter Property="VerticalAlignment" Value="Top"/>
<Setter Property="HorizontalAlignment" Value="Stretch"/>
<Setter Property="Background" Value="{StaticResource TitleBackground}"/>
<Setter Property="Padding" Value="25,0"/>
</Style>
<Style TargetType="TextBlock">
<Setter Property="VerticalAlignment" Value="Center"/>
<Setter Property="TextAlignment" Value="Center"/>
<Setter Property="FontSize" Value="48"/>
<Setter Property="Foreground" Value="{StaticResource TextForeground}"/>
</Style>
</ResourceDictionary>
Last, wrap your Border with it!
<local:BorderTheme>
<Border>
<TextBlock Text="TextBlock"/>
</Border>
</local:BorderTheme>
That's it. You should be able to see the styles applied to your Border as well as your TextBlock. :)