title: silverlight NaN height and width, ActualHeight and ActualWidth also return 0.0 - what is the workaround?
body: <p><code>popUpControl</code> and <code>listBoxControl</code> below are returning <code>NaN</code> as the height and width. The <code>ActualHeight</code> is also 0.0</p>
  
  <p>Why? and more importantly what is the workaround for this?</p>
  
  <pre><code>&lt;Popup Name="popUpControl" IsOpen="True" VerticalAlignment="Top" HorizontalAlignment="Left" &gt;
      &lt;ListBox Name="listBoxControl" SelectionChanged="_ListBox_SelectionChanged"
              Style="{StaticResource ListBoxStyle}" BorderBrush="Transparent"
               MaxHeight="300" MaxWidth="350" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch"&gt;
          &lt;ListBox.ItemTemplate&gt;
              &lt;DataTemplate&gt;
                  &lt;StackPanel Orientation="Horizontal" &gt;
                      &lt;TextBlock Text="{Binding ID}" VerticalAlignment="Center" Margin="2,0,0,0" /&gt;
                      &lt;TextBlock Text="{Binding Name}" VerticalAlignment="Center" Margin="2,0,0,0" /&gt;
                  &lt;/StackPanel&gt;
              &lt;/DataTemplate&gt;
          &lt;/ListBox.ItemTemplate&gt;
      &lt;/ListBox&gt;
  &lt;/Popup&gt;
  </code></pre>