在Silverlight中访问列表框中的父datacontext

<UserControl x:Name="root">
    <ListBox>
        <ListBox.DataContext>
           <Binding ElementName="root" Path="DataContext" />
        </ListBox.DataContext>
    </ListBox>
</UserControl>

<UserControl>
    <ListBox>
        <ListBox.DataContext>
           <Binding RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type UserControl}}" Path="DataContext" />
        </ListBox.DataContext>
    </ListBox>
</UserControl>

public class MyUserControl : UserControl
{
    public MyUserControl()
    {
        InitializeComponent();
        ListBox listBox = new ListBox();
        listBox.DataContext = this.DataContext;
    }
}