populate a wpf combo with data from XAML

[wpfRookie]

Hello,
I would like to populate a wpf combo box from a data island in XAML.
I adapted an example I found on the net, like so:

<Window.Resources>
<XmlDataProvider x:Key="GreekHeroesData" XPath="GreekHeroes/Hero">
<x:XData>
<GreekHeroes xmlns="">
<Hero Name="Jason" />
<Hero Name="Hercules" />
</GreekHeroes>
</x:XData>
</XmlDataProvider>
</Window.Resources>

<ComboBox ItemsSource="{Binding Source={StaticResource GreekHeroesData}}"

</ComboBox>

</Window>

But the combo stays empty. What is wrong here?

Thanks for your help.
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