silverlight 2 binding data to transforms?

I am working on creating a tag cloud in Silverlight 2 and trying to bind data from a List collection to a Scale transform on a TextBlock. When running this I get an AG_E_PARSER_BAD_PROPERTY_VALUE error. Is it possible to data bind values to transforms in Silverlight 2? If not could I do something to the effect of FontSize={Binding Weight*18} to multiply the tag's weight by a base font size? I know this won't work, but what is the best way to calculate property values for items in a DataTemplate?

<DataTemplate>
<TextBlock HorizontalAlignment="Stretch" VerticalAlignment="Stretch" TextWrapping="Wrap" d:IsStaticText="False" Text="{Binding Path=Text}" Foreground="#FF1151A8" FontSize="18" UseLayoutRounding="False" Margin="4,4,4,4" RenderTransformOrigin="0.5,0.5">
<TextBlock.RenderTransform>
 <TransformGroup>
  <ScaleTransform ScaleX="{Binding Path=WeightPlusOne}" ScaleY="{Binding Path=WeightPlusOne}"/>
 </TransformGroup>
</TextBlock.RenderTransform>

From stackoverflow

• The issue seems to be Rule #1 from this post:

  The target of data binding must be a FrameworkElement.

  So since ScaleTransform isn't a FrameworkElement it doesn't support binding. I tried to bind to a SolidColorBrush to test this out and got the same error as with the ScaleTransform.

  So in order to get around this you can create a control that exposes a dependency property of your tag data type. Then have a property changed event that binds the properties of your tag data to the properties in the control (one of which would be the scale transform). Here is the code I used to test this out.

  items control:

  <ItemsControl x:Name="items">
    <ItemsControl.ItemTemplate>
      <DataTemplate>
         <local:TagControl TagData="{Binding}" />
      </DataTemplate>
    </ItemsControl.ItemTemplate>
  </ItemsControl>
  

  tag control xaml:

  <UserControl x:Class="SilverlightTesting.TagControl"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
      >
      <TextBlock x:Name="text" TextWrapping="Wrap" FontSize="18" Margin="4,4,4,4">
        <TextBlock.RenderTransform>
            <ScaleTransform x:Name="scaleTx" />
        </TextBlock.RenderTransform>
      </TextBlock>
  </UserControl>
  

  tag control code:

  public partial class TagControl : UserControl
  {
      public TagControl()
      {
          InitializeComponent();
      }
  
      public Tag TagData
      {
          get { return (Tag)GetValue(TagDataProperty); }
          set { SetValue(TagDataProperty, value); }
      }
  
      // Using a DependencyProperty as the backing store for TagData.  This enables animation, styling, binding, etc...
      public static readonly DependencyProperty TagDataProperty =
          DependencyProperty.Register("TagData", typeof(Tag), typeof(TagControl), new PropertyMetadata(new PropertyChangedCallback(TagControl.OnTagDataPropertyChanged)));
  
      public static void OnTagDataPropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
      {
          var tc = obj as TagControl;
          if (tc != null) tc.UpdateTagData();
      }
  
      public void UpdateTagData()
      {
          text.Text = TagData.Title;
          scaleTx.ScaleX = scaleTx.ScaleY = TagData.Weight;
          this.InvalidateMeasure();
      }
  
  }
  

  Seems like overkill for just setting a single property, but I couldn't find an easier way.

• How do you get the TagControl to acces scaleTx?