TreeView WPF C# отображение содержимого файлов по критерию в виде дерева

Всем привет написал такой код, но почему то не отображается ничего, хотя на пером этапе в _currDirectory лежит 16 обьектов. Хелп

public abstract class NotifyPropertyChanged : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
 public abstract class TreeNode : NotifyPropertyChanged
    {
        protected string _nodeName;
        protected ObservableCollection<TreeNode> _items;

        public string NodeName
        {
            get => _nodeName;
            set
            {
                _nodeName = value;
                OnPropertyChanged();
            }
        }

        public ObservableCollection<TreeNode> Items
        {
            get => _items;
            set
            {
                _items = value;
                OnPropertyChanged();
            }
        }
    }

public class DirectoryNode : TreeNode
    {
        public DirectoryNode()
        {
            _items = new System.Collections.ObjectModel.ObservableCollection<TreeNode>();
        }
    }

public class FileNode : TreeNode
    {
        public FileNode() 
        {
            _items = new System.Collections.ObjectModel.ObservableCollection<TreeNode>();
        }
    }

 public class Seeker
    {
        private Thread _thread;
        private ManualResetEventSlim _event = new ManualResetEventSlim(false);
        private uint _countFound = 0;
        private uint _allCountFound = 0;
        private Regex _format = new Regex(string.Empty);
        private DirectoryNode _startDirectory;
        private DirectoryNode _currDirectory;
        private Stack<DirectoryNode> _nodes;

        public uint Found { get => _countFound; }
        public uint AllFound { get => _allCountFound; }
        public string Format { set => _format = new Regex(Regex.Escape(value)); }
        public string StartDirectory { set => _startDirectory = new DirectoryNode { NodeName = value }; }
        public string CurrentDirectory { get => _currDirectory.NodeName; }

        public Seeker() { }

        public void Seek()
        {
            Restart();
            _thread = new Thread(()
                => Seeking()) { IsBackground = true };
            _thread.Start();
        }

        private void Restart()
        {
            _nodes = new Stack<DirectoryNode>();
            _currDirectory = _startDirectory;
            _countFound = 0;
            _allCountFound = 0;
        }

        private void Seeking()
        {
            _nodes.Push(_startDirectory);

            while (CheckStop())
            {
                _currDirectory = _nodes.Pop();
                CheckDirectory();
                CheckFiles();
            }
        }

        private void CheckFiles()
        {
            var currDirInfo = new DirectoryInfo(_currDirectory.NodeName);
            foreach (var file in currDirInfo.GetFiles())
            {
                _allCountFound++;
                if (_format.IsMatch(file.Name))
                {
                    _countFound++;
                    _currDirectory.Items.Add(new FileNode { NodeName = file.Name });
                }    
            }
        }

        private void CheckDirectory()
        {
            var currDirInfo = new DirectoryInfo(_currDirectory.NodeName);
            foreach (var dir in currDirInfo.GetDirectories())
            {
                _currDirectory.Items.Add(new DirectoryNode { NodeName = dir.Name });
            }
        }

        private bool CheckStop() => _nodes.Count > 0;
    }

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            var seeker = new Seeker();
            seeker.Format = "*.txt";
            seeker.StartDirectory = @"c:\";
            seeker.Seek();
        }
    }

MainWindow.xaml

<Window x:Class="FileSearch.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:FileSearch"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <TreeView ItemsSource="{Binding TreeNodes}">
            <TreeView.Resources>
                <HierarchicalDataTemplate DataType="{x:Type local:FileNode}" ItemsSource="{Binding Items}">
                    <TextBlock Text="{Binding NodeName}" />
                </HierarchicalDataTemplate>
                <HierarchicalDataTemplate DataType="{x:Type local:DirectoryNode}" ItemsSource="{Binding Items}">
                    <TextBlock Text="{Binding NodeName,StringFormat=[{0}]}" />
                </HierarchicalDataTemplate>
            </TreeView.Resources>
        </TreeView>
    </Grid>
</Window>