WPF Data Binding between a tab control and a tree view

I am getting back to learning WPF and am writing a very simple application. In this application a tab control displays note tabs for the selected item in a tree view control, using a binding to a property of that items which contains an observable collection. Unfortunately, when I select an item, even when the item has objects in its property that the tab control is bound to, no tabs appear.

I have a tree view control name nodeTreeView.
I have a tab control name noteTabs.
The tree view controls has an items source of ObservableCollection<Node>.
The tab control has an items source of {Binding Source=nodeTreeView, Path=SelectedItem.Notes}
Notes is a property of Node containing an observable collection<Note>.

I have gotten the tab control to display items before when I used a specific items source. But now that I have used a binding to point to a collection in a property of the selected item of the tree view control, it doesn't work.

Does anyone have any idea?

I will post the code below but please understand that since I simply slapped it together for the purpose of learning that it is very sloppy.

Code:

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<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication1"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto">
            </RowDefinition>
            <RowDefinition></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
        </Grid.RowDefinitions>
        <Menu Grid.Row="0">
            <MenuItem Header="File">
                <MenuItem Header="New"></MenuItem>
                <Separator/>
                <MenuItem Header="Save"></MenuItem>
                <MenuItem Header="Save As"></MenuItem>
                <Separator/>
                <MenuItem Header="Exit"></MenuItem>
            </MenuItem>
        </Menu>
        <Grid Grid.Row="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>
            <TreeView x:Name="nodeTreeView" Grid.Column="0" HorizontalAlignment="Stretch">
                <TreeView.ItemTemplate>
                    <HierarchicalDataTemplate ItemsSource="{Binding Path=Children}">
                        <TextBlock Text="{Binding Path=Title}"></TextBlock>
                    </HierarchicalDataTemplate>
                </TreeView.ItemTemplate>
            </TreeView>
            <GridSplitter Width="5" HorizontalAlignment="Stretch" Grid.Column="1"></GridSplitter>
            <TabControl x:Name="noteTabs"
                        HorizontalAlignment="Stretch"
                        VerticalAlignment="Stretch" Grid.Column="2"
                        ItemsSource="{Binding Source=nodeTreeView, Path=SelectedItem.Notes}">
                <TabControl.ContentTemplate>
                    <DataTemplate>
                        <TextBox Text="{Binding Path=Text, Mode=TwoWay}"></TextBox>
                    </DataTemplate>
                </TabControl.ContentTemplate>
                <TabControl.ItemTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding Path=Title}"></TextBlock>
                    </DataTemplate>
                </TabControl.ItemTemplate>
            </TabControl>
        </Grid>
        <StatusBar Grid.Row="2">
            <StatusBarItem Content="Yo"></StatusBarItem>
        </StatusBar>
    </Grid>
</Window>

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Code:

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using System;
using System.ComponentModel;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            ObservableCollection<Node> nodes = new ObservableCollection<Node>();
            nodes.Add(new Node("Root"));
            nodes[0].Children.Add(new Node("Node 1"));
            nodes[0].Children.Add(new Node("Node 2"));

            nodeTreeView.ItemsSource = nodes;
           
            var notes = nodes[0].Children[0].Notes;
            notes.Add(new Note("Note 1", "This is the first note."));
            notes.Add(new Note("Note 2", "This is the second note."));

           
        }
    }

    public class Node : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public ObservableCollection<Node> Children { get; }
        public ObservableCollection<Note> Notes { get; }

        public Node(string title)
        {
            Title = title;
            Children = new ObservableCollection<Node>();
            Notes = new ObservableCollection<Note>();
        }

        private string _title;

        public string Title
        {
            get
            {
                return _title;
            }

            set
            {
                if (_title != value)
                {
                    _title = value;
                    NotifyPropertyChanged(nameof(Title));
                }
            }
        }

        private void NotifyPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }

    public class Note : INotifyPropertyChanged
    {
        private string _title;
        private string _text;

        public string Title
        {
            get
            {
                return _title;
            }

            set
            {
                if (_title != value)
                {
                    _title = value;
                    NotifyPropertyChanged(nameof(Title));
                }
            }
        }

        public string Text
        {
            get
            {
                return _text;
            }

            set
            {
                if (_text != value)
                {
                    _text = value;
                    NotifyPropertyChanged(nameof(Text));
                }
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;

        public Note(string title, string text)
        {
            Title = title;
            Text = text;
        }

        private void NotifyPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

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What is the value for SelectedItem.Notes?