Silverlight data bind combobox items and value separately

I can use databinding to bind the 开发者_运维问答contents of a combobox to a collection, or I can bind the selected value in the combobox to a member of a class, but I can't do both at the same time. I want to be able to bind the contents to one thing and the selected value to something else, I guess the combobox can't handle two datacontexts or I'm not specifying them explicitly. Example below, I'd appreciate any help! Thanks.

In XAML:

<ComboBox Name="Combo" ItemsSource="{Binding}" 
          SelectedValue="{Binding ID, Mode=TwoWay}"/>

In code:

LayoutRoot.DataContext = myClass;
Combo.DataContext = items;

This should do it for you, or at least be close.

<Grid DataContext="{Binding Source=MyObject}">
    <ComboBox x:Name="Combo"
              ItemsSource="{Binding Source=MyCollection}"
              SelectedValue="{Binding Path=ID, Mode=TwoWay}"/>
</Grid>