Her's what I want: A listbox whose items consist of a stackpanel with two textblocks. The textblocks need to support wrapping, the listbox should not expand, and there should be no horizontal scrollbar. Here's the code I have so far. Copy and paste it into XamlPad and you'll see what I'm talking about.

<ListBox Height="300" Width="300" x:Name="tvShows">
    <ListBox.Items>
        <ListBoxItem>
            <StackPanel>
                <TextBlock Width="{Binding ElementName=tvShows, Path=ActualWidth}" TextWrapping="Wrap">Lost is an American live-action television series. It follows the lives of plane crash survivors on a mysterious tropical island.</TextBlock>
                <TextBlock Width="{Binding ElementName=tvShows, Path=ActualWidth}" TextWrapping="Wrap">Lost is an American live-action television series. It follows the lives of plane crash survivors on a mysterious tropical island.</TextBlock>
            </StackPanel>
        </ListBoxItem>
        <ListBoxItem>
            <StackPanel>
                <TextBlock Width="{Binding ElementName=tvShows, Path=ActualWidth}" TextWrapping="Wrap">Lost is an American live-action television series. It follows the lives of plane crash survivors on a mysterious tropical island.</TextBlock>
                <TextBlock Width="{Binding ElementName=tvShows, Path=ActualWidth}" TextWrapping="Wrap">Lost is an American live-action television series. It follows the lives of plane crash survivors on a mysterious tropical island.</TextBlock>
            </StackPanel>
        </ListBoxItem>
    </ListBox.Items>
</ListBox>

This seems to be doing the job of keeping the textblocks from growing, but there's one problem. The textblocks seem to be slightly larger than the listbox, causing the horizontal scrollbar to appear. This is strange because their widths are bound to the lisbox's ActualWidth. Also, if you add a few more items to the listbox (just cut and paste in XamlPad) causing the vertical scrollbar to appear, the width of the textblocks do not resize to the vertical scrollbar.

How do I keep the textblocks inside the listbox, with or without the vertical scrollbar?