public class BindableStaticResource : StaticResourceExtension
    {
        public Binding Binding { get; set; }

        public BindableStaticResource()
        {
        }

        public BindableStaticResource(Binding binding)
        {
            Binding = binding;
        }
    }

    public abstract class TreeItem<T>
    {
        private bool _isSelected;
        private bool _isExpanded;

        public bool IsSelected
        {
            set
            { 
                _isSelected = value;
                MessageBox.Show("Элемент дерева выделился");
            }
            get { return _isSelected; }
        }

        public bool IsExpanded
        {
            set
            {
                _isExpanded = value;
                MessageBox.Show("Ветка дерева раскрылась");
            }
            get { return _isExpanded; }
        }

        public abstract ObservableCollection<T> Children { set; get; }
    }
    
    public class Person : TreeItem<Person>
    {
        public string Name { set; get; }
        public int Age { set; get; }
        public override ObservableCollection<Person> Children { set; get; }
    }



    static class DataLoader
    {
        public static ObservableCollection<Person> GetPersonList()
        {
            var result = new ObservableCollection<Person>
            {
                new Person
                {
                    Name = "Roman Mejtes",
                    Age = 30,
                    Children = new ObservableCollection<Person>
                    {
                        new Person
                        {
                            Name = "Olga Mejtes", 
                            Age = 5
                        }
                    }
                },
                new Person
                {
                    Name = "Sofia Nesterova",
                    Age = 34,
                    Children = new ObservableCollection<Person>
                    {
                        new Person
                        {
                            Name = "Aleksandr Nesterov", 
                            Age = 12
                        }
                    }
                }
            };
            return result;
        }

    }
    class Data
    {
        private readonly ObservableCollection<Person> _persons;

        public ObservableCollection<Person> Persons
        {
            get { return _persons; }
        }

        public Data()
        {
            _persons = new ObservableCollection<Person>(DataLoader.GetPersonList());
        }
        
    }

<Window x:Class="WpfApplication9.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:my="clr-namespace:WpfApplication9"
        Title="MainWindow" Height="350" Width="525"
        x:Name="Window">
    <Window.Resources>
        <Style x:Key="ProjectStyle" TargetType="{x:Type TextBlock}">
            <Setter Property="Background" Value="Firebrick"/>
            <Setter Property="Foreground" Value="White"/>
            <Setter Property="FontSize" Value="20"/>
            <Setter Property="Padding" Value="5,5,5,5"/>
            <Setter Property="Margin" Value="5,5,5,5"/>

            <Style.Triggers>
                <Trigger Property="IsFocused" Value="True">
                    <Setter Property="Background" Value="Firebrick"/>
                    <Setter Property="Foreground" Value="White"/>
                </Trigger>
                <Trigger Property="IsFocused" Value="False"> 
                    <Setter Property="Background" Value="White"/>
                    <Setter Property="Foreground" Value="Firebrick"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <Grid>
        <TreeView x:Name="ProjTreeView" ItemsSource="{Binding Persons}"> 
            <TreeView.Resources>
                <Style TargetType="{x:Type TreeViewItem}">
                    <EventSetter Event="GotFocus" Handler="EventSetter_OnHandler"/>
                    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
                    <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
                </Style>
                <HierarchicalDataTemplate DataType="{x:Type my:Person}" ItemsSource="{Binding Children}">
                    <TextBlock Text="{Binding Name}" Style="{StaticResource ProjectStyle}"/>
                </HierarchicalDataTemplate>
            </TreeView.Resources>
        </TreeView>
    </Grid>
</Window>

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void EventSetter_OnHandler(object sender, RoutedEventArgs e)
        {
            MessageBox.Show("Событие GotFocus возбудилось");
        }
    }

<Window x:Class="WpfApplication9.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:my="clr-namespace:WpfApplication9"
        Title="MainWindow" Height="350" Width="525"
        x:Name="Window">
    <Grid>
        <TreeView x:Name="ProjTreeView" ItemsSource="{Binding Persons}"> 
            <TreeView.Resources>
                <Style TargetType="{x:Type TreeViewItem}">
                    <EventSetter Event="GotFocus" Handler="EventSetter_OnHandler"/>
                    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
                    <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
                    <Setter Property="FontSize" Value="16"/>
                    <Setter Property="FontWeight" Value="Normal"/>
                    <Style.Triggers>
                        <Trigger Property="IsSelected" Value="True">
                            <Setter Property="FontSize" Value="20"/>
                            <Setter Property="FontWeight" Value="ExtraBold"/>
                        </Trigger>
                    </Style.Triggers>
                </Style>
                <HierarchicalDataTemplate DataType="{x:Type my:Person}" ItemsSource="{Binding Children}">
                    <HierarchicalDataTemplate.Resources>
                        <Style TargetType="TreeViewItem">
                            <Setter Property="FontSize" Value="14"/>
                        </Style>
                    </HierarchicalDataTemplate.Resources>
                    <TextBlock x:Name="TextBlock" Text="{Binding Name}" Margin="2" />
                </HierarchicalDataTemplate>
            </TreeView.Resources>
        </TreeView>
    </Grid>
</Window>