diff --git a/demo/Semi.Avalonia.TreeDataGrid.Demo/MainWindow.axaml b/demo/Semi.Avalonia.TreeDataGrid.Demo/MainWindow.axaml
index a86cfd2..32c5e1d 100644
--- a/demo/Semi.Avalonia.TreeDataGrid.Demo/MainWindow.axaml
+++ b/demo/Semi.Avalonia.TreeDataGrid.Demo/MainWindow.axaml
@@ -112,10 +112,18 @@
                                             </MultiBinding>
                                         </Image.Source>
                                     </Image>
-                                    <TextBox VerticalAlignment="Center" Text="{Binding Name}" />
+                                    <TextBox
+                                        VerticalAlignment="Center"
+                                        Classes="Small"
+                                        Text="{Binding Name}">
+                                        <TextBox.Styles>
+                                            <Style Selector="DataValidationErrors">
+                                                <Setter Property="Theme" Value="{DynamicResource TooltipDataValidationErrors}" />
+                                            </Style>
+                                        </TextBox.Styles>
+                                    </TextBox>
                                 </StackPanel>
                             </DataTemplate>
-
                         </TreeDataGrid.Resources>
                         <TreeDataGrid.Styles>
                             <Style Selector="TreeDataGrid TreeDataGridRow:nth-child(2n)">
diff --git a/demo/Semi.Avalonia.TreeDataGrid.Demo/ViewModels/FilesPageViewModel.cs b/demo/Semi.Avalonia.TreeDataGrid.Demo/ViewModels/FilesPageViewModel.cs
index f80e633..3349363 100644
--- a/demo/Semi.Avalonia.TreeDataGrid.Demo/ViewModels/FilesPageViewModel.cs
+++ b/demo/Semi.Avalonia.TreeDataGrid.Demo/ViewModels/FilesPageViewModel.cs
@@ -171,219 +171,216 @@ public class FilesPageViewModel: ObservableObject
 public class FileNodeViewModel: ObservableObject, IEditableObject
 {
     private string _path;
-        private string _name;
-        private string? _undoName;
-        private long? _size;
-        private DateTimeOffset? _modified;
-        private FileSystemWatcher? _watcher;
-        private ObservableCollection<FileNodeViewModel>? _children;
-        private bool _hasChildren = true;
-        private bool _isExpanded;
+    private string _name;
+    private string? _undoName;
+    private long? _size;
+    private DateTimeOffset? _modified;
+    private FileSystemWatcher? _watcher;
+    private ObservableCollection<FileNodeViewModel>? _children;
+    private bool _hasChildren = true;
+    private bool _isExpanded;
 
-        public FileNodeViewModel(
-            string path,
-            bool isDirectory,
-            bool isRoot = false)
+    public FileNodeViewModel( string path, bool isDirectory, bool isRoot = false)
+    {
+        _path = path;
+        _name = isRoot ? path : System.IO.Path.GetFileName(Path);
+        _isExpanded = isRoot;
+        IsDirectory = isDirectory;
+        HasChildren = isDirectory;
+
+        if (!isDirectory)
         {
-            _path = path;
-            _name = isRoot ? path : System.IO.Path.GetFileName(Path);
-            _isExpanded = isRoot;
-            IsDirectory = isDirectory;
-            HasChildren = isDirectory;
+            var info = new FileInfo(path);
+            Size = info.Length;
+            Modified = info.LastWriteTimeUtc;
+        }
+    }
 
-            if (!isDirectory)
-            {
-                var info = new FileInfo(path);
-                Size = info.Length;
-                Modified = info.LastWriteTimeUtc;
-            }
+    public string Path 
+    {
+        get => _path;
+        private set => SetProperty(ref _path, value);
+    }
+
+    public string Name 
+    {
+        get => _name;
+        private set => SetProperty(ref _name, value);
+    }
+
+    public long? Size 
+    {
+        get => _size;
+        private set => SetProperty(ref _size, value);
+    }
+
+    public DateTimeOffset? Modified 
+    {
+        get => _modified;
+        private set => SetProperty(ref _modified, value);
+    }
+
+    public bool HasChildren
+    {
+        get => _hasChildren;
+        private set => SetProperty(ref _hasChildren, value);
+    }
+
+    public bool IsExpanded
+    {
+        get => _isExpanded;
+        set => SetProperty(ref _isExpanded, value);
+    }
+
+    public bool IsChecked { get; set; }
+    public bool IsDirectory { get; }
+    public IReadOnlyList<FileNodeViewModel> Children => _children ??= LoadChildren();
+
+    private ObservableCollection<FileNodeViewModel> LoadChildren()
+    {
+        if (!IsDirectory)
+        {
+            throw new NotSupportedException();
         }
 
-        public string Path 
+        var options = new EnumerationOptions { IgnoreInaccessible = true };
+        var result = new ObservableCollection<FileNodeViewModel>();
+
+        foreach (var d in Directory.EnumerateDirectories(Path, "*", options))
         {
-            get => _path;
-            private set => SetProperty(ref _path, value);
+            result.Add(new FileNodeViewModel(d, true));
         }
 
-        public string Name 
+        foreach (var f in Directory.EnumerateFiles(Path, "*", options))
         {
-            get => _name;
-            private set => SetProperty(ref _name, value);
+            result.Add(new FileNodeViewModel(f, false));
         }
 
-        public long? Size 
+        _watcher = new FileSystemWatcher
         {
-            get => _size;
-            private set => SetProperty(ref _size, value);
-        }
+            Path = Path,
+            NotifyFilter = NotifyFilters.FileName | NotifyFilters.Size | NotifyFilters.LastWrite,
+        };
 
-        public DateTimeOffset? Modified 
+        _watcher.Changed += OnChanged;
+        _watcher.Created += OnCreated;
+        _watcher.Deleted += OnDeleted;
+        _watcher.Renamed += OnRenamed;
+        _watcher.EnableRaisingEvents = true;
+
+        if (result.Count == 0)
+            HasChildren = false;
+
+        return result;
+    }
+
+    public static Comparison<FileNodeViewModel?> SortAscending<T>(Func<FileNodeViewModel, T> selector)
+    {
+        return (x, y) =>
         {
-            get => _modified;
-            private set => SetProperty(ref _modified, value);
-        }
+            if (x is null && y is null)
+                return 0;
+            else if (x is null)
+                return -1;
+            else if (y is null)
+                return 1;
+            if (x.IsDirectory == y.IsDirectory)
+                return Comparer<T>.Default.Compare(selector(x), selector(y));
+            else if (x.IsDirectory)
+                return -1;
+            else
+                return 1;
+        };
+    }
 
-        public bool HasChildren
+    public static Comparison<FileNodeViewModel?> SortDescending<T>(Func<FileNodeViewModel, T> selector)
+    {
+        return (x, y) =>
         {
-            get => _hasChildren;
-            private set => SetProperty(ref _hasChildren, value);
-        }
+            if (x is null && y is null)
+                return 0;
+            else if (x is null)
+                return 1;
+            else if (y is null)
+                return -1;
+            if (x.IsDirectory == y.IsDirectory)
+                return Comparer<T>.Default.Compare(selector(y), selector(x));
+            else if (x.IsDirectory)
+                return -1;
+            else
+                return 1;
+        };
+    }
 
-        public bool IsExpanded
-        {
-            get => _isExpanded;
-            set => SetProperty(ref _isExpanded, value);
-        }
+    void IEditableObject.BeginEdit() => _undoName = _name;
+    void IEditableObject.CancelEdit() => _name = _undoName!;
+    void IEditableObject.EndEdit() => _undoName = null;
 
-        public bool IsChecked { get; set; }
-        public bool IsDirectory { get; }
-        public IReadOnlyList<FileNodeViewModel> Children => _children ??= LoadChildren();
-
-        private ObservableCollection<FileNodeViewModel> LoadChildren()
-        {
-            if (!IsDirectory)
-            {
-                throw new NotSupportedException();
-            }
-
-            var options = new EnumerationOptions { IgnoreInaccessible = true };
-            var result = new ObservableCollection<FileNodeViewModel>();
-
-            foreach (var d in Directory.EnumerateDirectories(Path, "*", options))
-            {
-                result.Add(new FileNodeViewModel(d, true));
-            }
-
-            foreach (var f in Directory.EnumerateFiles(Path, "*", options))
-            {
-                result.Add(new FileNodeViewModel(f, false));
-            }
-
-            _watcher = new FileSystemWatcher
-            {
-                Path = Path,
-                NotifyFilter = NotifyFilters.FileName | NotifyFilters.Size | NotifyFilters.LastWrite,
-            };
-
-            _watcher.Changed += OnChanged;
-            _watcher.Created += OnCreated;
-            _watcher.Deleted += OnDeleted;
-            _watcher.Renamed += OnRenamed;
-            _watcher.EnableRaisingEvents = true;
-
-            if (result.Count == 0)
-                HasChildren = false;
-
-            return result;
-        }
-
-        public static Comparison<FileNodeViewModel?> SortAscending<T>(Func<FileNodeViewModel, T> selector)
-        {
-            return (x, y) =>
-            {
-                if (x is null && y is null)
-                    return 0;
-                else if (x is null)
-                    return -1;
-                else if (y is null)
-                    return 1;
-                if (x.IsDirectory == y.IsDirectory)
-                    return Comparer<T>.Default.Compare(selector(x), selector(y));
-                else if (x.IsDirectory)
-                    return -1;
-                else
-                    return 1;
-            };
-        }
-
-        public static Comparison<FileNodeViewModel?> SortDescending<T>(Func<FileNodeViewModel, T> selector)
-        {
-            return (x, y) =>
-            {
-                if (x is null && y is null)
-                    return 0;
-                else if (x is null)
-                    return 1;
-                else if (y is null)
-                    return -1;
-                if (x.IsDirectory == y.IsDirectory)
-                    return Comparer<T>.Default.Compare(selector(y), selector(x));
-                else if (x.IsDirectory)
-                    return -1;
-                else
-                    return 1;
-            };
-        }
-
-        void IEditableObject.BeginEdit() => _undoName = _name;
-        void IEditableObject.CancelEdit() => _name = _undoName!;
-        void IEditableObject.EndEdit() => _undoName = null;
-
-        private void OnChanged(object sender, FileSystemEventArgs e)
-        {
-            if (e.ChangeType == WatcherChangeTypes.Changed && File.Exists(e.FullPath))
-            {
-                Dispatcher.UIThread.Post(() =>
-                {
-                    foreach (var child in _children!)
-                    {
-                        if (child.Path == e.FullPath)
-                        {
-                            if (!child.IsDirectory)
-                            {
-                                var info = new FileInfo(e.FullPath);
-                                child.Size = info.Length;
-                                child.Modified = info.LastWriteTimeUtc;
-                            }
-                            break;
-                        }
-                    }
-                });
-            }
-        }
-
-        private void OnCreated(object sender, FileSystemEventArgs e)
-        {
-            Dispatcher.UIThread.Post(() =>
-            {
-                var node = new FileNodeViewModel(
-                    e.FullPath,
-                    File.GetAttributes(e.FullPath).HasFlag(FileAttributes.Directory));
-                _children!.Add(node);
-            });
-        }
-
-        private void OnDeleted(object sender, FileSystemEventArgs e)
-        {
-            Dispatcher.UIThread.Post(() =>
-            {
-                for (var i = 0; i < _children!.Count; ++i)
-                {
-                    if (_children[i].Path == e.FullPath)
-                    {
-                        _children.RemoveAt(i);
-                        System.Diagnostics.Debug.WriteLine($"Removed {e.FullPath}");
-                        break;
-                    }
-                }
-            });
-        }
-
-        private void OnRenamed(object sender, RenamedEventArgs e)
+    private void OnChanged(object sender, FileSystemEventArgs e)
+    {
+        if (e.ChangeType == WatcherChangeTypes.Changed && File.Exists(e.FullPath))
         {
             Dispatcher.UIThread.Post(() =>
             {
                 foreach (var child in _children!)
                 {
-                    if (child.Path == e.OldFullPath)
+                    if (child.Path == e.FullPath)
                     {
-                        child.Path = e.FullPath;
-                        child.Name = e.Name ?? string.Empty;
+                        if (!child.IsDirectory)
+                        {
+                            var info = new FileInfo(e.FullPath);
+                            child.Size = info.Length;
+                            child.Modified = info.LastWriteTimeUtc;
+                        }
                         break;
                     }
                 }
             });
         }
+    }
+
+    private void OnCreated(object sender, FileSystemEventArgs e)
+    {
+        Dispatcher.UIThread.Post(() =>
+        {
+            var node = new FileNodeViewModel(
+                e.FullPath,
+                File.GetAttributes(e.FullPath).HasFlag(FileAttributes.Directory));
+            _children!.Add(node);
+        });
+    }
+
+    private void OnDeleted(object sender, FileSystemEventArgs e)
+    {
+        Dispatcher.UIThread.Post(() =>
+        {
+            for (var i = 0; i < _children!.Count; ++i)
+            {
+                if (_children[i].Path == e.FullPath)
+                {
+                    _children.RemoveAt(i);
+                    System.Diagnostics.Debug.WriteLine($"Removed {e.FullPath}");
+                    break;
+                }
+            }
+        });
+    }
+
+    private void OnRenamed(object sender, RenamedEventArgs e)
+    {
+        Dispatcher.UIThread.Post(() =>
+        {
+            foreach (var child in _children!)
+            {
+                if (child.Path == e.OldFullPath)
+                {
+                    child.Path = e.FullPath;
+                    child.Name = e.Name ?? string.Empty;
+                    break;
+                }
+            }
+        });
+    }
 }
 
 internal static class ListExtensions