<TreeView> <TreeView.ItemContainerStyle> <Style TargetType="TreeViewItem"> <Setter Property="IsExpanded" Value="True"/> </Style> </TreeView>
<TreeView ItemsSource={Binding Persons}> <TreeView.ItemContainerStyle> <Style TargetType="TreeViewItem"> <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" /> </Style> </TreeView>