I found you can just set d:DataContext
on the root element inside the DataTemplate
.
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
<ListBox ItemsSource="{Binding People}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel d:DataContext="{d:DesignInstance Type=local:Person}">
<TextBlock Text="{Binding Name}" />
<TextBlock Text="{Binding Age}" />
<TextBlock Text="{Binding Height}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>