Silverlight从URL加载图像,但不显示

请看以下XAML:

<Grid>
<HyperlinkButton x:Name="Link" Background="Green">
    <Grid Background="Red">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto" />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="12" />
        </Grid.RowDefinitions>
        <Image x:Name="AvatarImage" Style="{StaticResource AvatarStyle}" Grid.Column="0" Grid.Row="0" />
        <StackPanel Grid.Column="1" HorizontalAlignment="Stretch">
            <TextBlock Text="New Topic" Style="{StaticResource ItemTypeStyle}" />
            <TextBlock x:Name="Title" Style="{StaticResource HeadlineStyle}" TextWrapping="Wrap" />
            <TextBlock x:Name="SubText" Style="{StaticResource TextStyle}" TextWrapping="Wrap" />
        </StackPanel>
        <TextBlock x:Name="TimeStampText" Grid.ColumnSpan="2" Grid.Row="1" Style="{StaticResource TimeStampStyle}" />
    </Grid>
</HyperlinkButton>

在用户控件的Loaded事件中,我调用以下代码:

var imageUrl = new Uri("http://coasterbuzz.com/Forums/UserAvatar.ashx?id=2");
AvatarImage.Source = new BitmapImage(imageUrl);

看着Firebug,图像从电线上掉了下来,但出于某种原因它没有显示出来。你猜为什么?您可能希望看到样式,但请注意,如果删除样式,则不会发生任何更改。