Silverlight - Binding ImageSource to Rectangle Fill

Question

Blend 4 is telling me this is invalid markup and its not telling me why:

<ImageBrush Stretch="Fill"  ImageSource="{Binding Avatar, Mode=OneWay}"/>

I'm pulling data from a Twitter feed, saving to an ImageSource, and then binding it to an ImageBrush(as seen below) to be used as the Fill for a Rectangle. Here is more context:

<Rectangle x:Name="Avatar" RadiusY="9" RadiusX="9" Width="45" Height="45"  VerticalAlignment="Center" HorizontalAlignment="Center" >
    <Rectangle.Fill>
       <ImageBrush Stretch="Fill"  ImageSource="{Binding Avatar, Mode=OneWay}"/>
    </Rectangle.Fill>
</Rectangle>

I'm using this inside of a Silverlight UserControl, which is used inside of a Silverlight Application. Any Ideas on what the problem could be?

Answer 1

Binding cannot be applied to an ImageBrush's ImageSource, or so it seems. I'm having a similar issue and looking for alternatives.