C#のWPFでファイルマネージャを作る：データバインディングで作り直し

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.IO;
using System.Runtime.CompilerServices;

namespace FileListViewDemo;

public class DirectoryItem : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler? PropertyChanged;
    protected void OnPropertyChanged([CallerMemberName] string? name = null)
        => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));

    public string Name { get; set; } = "";
    public string FullPath { get; set; } = "";
    public bool HasDummy { get; set; }
    public ObservableCollection<DirectoryItem> Children { get; } = [];

    private bool _isExpanded;
    public bool IsExpanded
    {
        get => _isExpanded;
        set
        {
            if (_isExpanded == value) return;
            _isExpanded = value;
            OnPropertyChanged();

            if (value)
            {
                LoadChildren();
            }
        }
    }

    private void LoadChildren()
    {
        if (!HasDummy) return;

        HasDummy = false;

        Children.Clear();

        try
        {
            foreach (var dir in Directory.GetDirectories(FullPath))
            {
                try
                {
                    var attr = File.GetAttributes(dir);
                    if ((attr & (FileAttributes.Hidden | FileAttributes.System)) != 0)
                        continue;

                    var child = new DirectoryItem
                    {
                        Name = Path.GetFileName(dir),
                        FullPath = dir,
                        HasDummy = true,
                    };
                    child.Children.Add(new DirectoryItem()); // ダミー
                    Children.Add(child);
                }
                catch { }
            }
        }
        catch { }
    }
}

using System.Windows.Media;

using Maywork.WPF.Helpers;

namespace FileListViewDemo;
public class FileItem : IFileItem
{
    public string Path { get; set; } = "";
    public string DisplayName { get; set; } = "";
    public ImageSource? Icon { get; set; }
    public bool IsDirectory { get; set; }
}

using System.IO;
using Maywork.WPF.Helpers;

namespace FileListViewDemo;
public static class FileService
{
    public static IEnumerable<FileItem> GetFlieList(string path)
    {
        if (File.Exists(path))
            throw new ArgumentException($"{path} is file");
        if (!Directory.Exists(path))
            throw new ArgumentException($"{path} not exists");
        
        return Directory.EnumerateFileSystemEntries(path)
            .Select(file =>
            {
                try
                {
                    var attr = File.GetAttributes(file);
                    return (file, attr); // ← ValueTupleでOK
                }
                catch
                {
                    return ((string file, FileAttributes attr)?)null;
                }
            })
            .Where(x => x.HasValue &&
                (x.Value.attr & (FileAttributes.Hidden | FileAttributes.System)) == 0)
            .Select(x =>
            {
                var (file, attr) = x!.Value;

                return new FileItem()
                {
                    Path = file,
                    DisplayName = Path.GetFileName(file),
                    Icon = IconHelper.GetIconImageSource(file),

                    IsDirectory = (attr & FileAttributes.Directory) != 0
                };
            })
            .ToList();

    }
}

<Window x:Class="FileListViewDemo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:FileListViewDemo"
        xmlns:h="clr-namespace:Maywork.WPF.Helpers"
        Title="FileListView Demo" Height="450" Width="800">
    <Window.DataContext>
        <local:MainWindowViewModel/>
    </Window.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid Grid.Row="0">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="Auto"/>
            </Grid.ColumnDefinitions>
            <StackPanel
                Grid.Column="0"
                Orientation="Horizontal">
                <Button
                    Content="⇧"
                    FontSize="16"
                    Width="32"
                    ToolTip="親ディレクトリへ移動"
                    Margin="4"
                    Padding="2"
                    Command="{Binding MoveParentCommand}"/>
                </StackPanel>
            <TextBox
                Grid.Column="1"
                x:Name="AddressBar"
                Text="{Binding CurrentPath, Mode=OneWay}"
                VerticalAlignment="Center"
                FontSize="16"
                Margin="4"/>
            <StackPanel
                Grid.Column="2"
                Orientation="Horizontal">
                <Button
                    Content="↵"
                    FontSize="16"
                    Width="32"
                    ToolTip="アドレスバーのディレクトリへ移動"
                    Margin="4"
                    Padding="2"
                    Command="{Binding MoveFolderCommand}"
                    CommandParameter="{Binding Text, ElementName=AddressBar}"/>
            </StackPanel>            
        </Grid>
        <Grid Grid.Row="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="2*"/>
            </Grid.ColumnDefinitions>

            <TreeView
                ItemsSource="{Binding RootDirectories}"
                h:TreeViewSelectedItemBehavior.SelectedItemChangedCommand="{Binding NavigateCommand}"
                Margin="4">
                <TreeView.ItemContainerStyle>
                    <Style TargetType="TreeViewItem">
                        <Setter Property="FontSize" Value="16"/>
                    </Style>
                </TreeView.ItemContainerStyle>

                <TreeView.ItemTemplate>
                    <HierarchicalDataTemplate ItemsSource="{Binding Children}">
                        <TextBlock Text="{Binding Name}"/>
                    </HierarchicalDataTemplate>
                </TreeView.ItemTemplate>

            </TreeView>

            <!-- グリッドセパレータ -->
            <GridSplitter
                Grid.Column="1"
                Width="5"
                HorizontalAlignment="Center"
                VerticalAlignment="Stretch"
                Background="Gray"
                ShowsPreview="True"
                ResizeDirection="Columns"
                Margin="2"/>
            <ListView
                Grid.Column="2"
                ItemsSource="{Binding FileList}"
                SelectedItem="{Binding SelectedItem}"
                h:GridViewSort.Enable="True"
                h:ListViewItemDoubleClick.Enable="True"
                Margin="8">
                <ListView.ItemContainerStyle>
                    <Style TargetType="ListViewItem">
                        <Setter Property="FontSize" Value="14"/>
                        <Setter Property="Padding" Value="4"/>
                    </Style>
                </ListView.ItemContainerStyle>
                <ListView.ContextMenu>
                    <ContextMenu>

                        <MenuItem Header="開く"
                                Command="{Binding OpenCommand}"
                                CommandParameter="{Binding PlacementTarget.SelectedItem,
                                    RelativeSource={RelativeSource AncestorType=ContextMenu}}"/>

                        <MenuItem Header="フォルダを開く"
                                Command="{Binding OpenFolderCommand}"
                                CommandParameter="{Binding PlacementTarget.SelectedItem,
                                    RelativeSource={RelativeSource AncestorType=ContextMenu}}"/>

                    </ContextMenu>
                </ListView.ContextMenu>
                <ListView.View>
                    <GridView AllowsColumnReorder="False">
                        <GridViewColumn
                            Header="アイコン"
                            Width="48">
                            <GridViewColumn.CellTemplate>
                                <DataTemplate>
                                    <Image
                                        Source="{Binding Icon}"
                                        Width="24"
                                        Height="24"/>
                                </DataTemplate>
                            </GridViewColumn.CellTemplate>
                        </GridViewColumn>
                        <GridViewColumn
                            Header="名前"
                            Width="300"
                            DisplayMemberBinding="{Binding DisplayName}"/>
                    </GridView>
                </ListView.View>
            </ListView>
        </Grid>
    </Grid>
</Window>

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Diagnostics;
using System.IO;
using System.Runtime.CompilerServices;
using System.Windows.Input;
using Maywork.WPF.Helpers;

namespace FileListViewDemo;
public class MainWindowViewModel : INotifyPropertyChanged, INavigationViewModel<IFileItem>
{
#region
    public event PropertyChangedEventHandler? PropertyChanged;
    protected void OnPropertyChanged([CallerMemberName] string? name = null)
        => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
#endregion

    private ObservableCollection<FileItem> _FileList = [];
    public ObservableCollection<FileItem> FileList
    {
        get => _FileList;
        set
        {
            if (_FileList == value) return;
            _FileList = value;
            OnPropertyChanged();
        }
    }
    private FileItem? _SelectedItem;
    public FileItem? SelectedItem
    {
        get => _SelectedItem;
        set
        {
            if (_SelectedItem == value) return;
            _SelectedItem = value;
            OnPropertyChanged();
        }
    }
    private string _currentPath = "";
    public string CurrentPath
    {
        get => _currentPath;
        set
        {
            if (_currentPath == value) return;
            _currentPath = value;
            OnPropertyChanged();
        }
    }
    public ObservableCollection<DirectoryItem> RootDirectories { get; } = [];


    public ICommand OpenCommand { get; }
    public ICommand OpenFolderCommand { get; }
    public ICommand MoveFolderCommand { get; }
    public ICommand MoveParentCommand { get; }
    public ICommand NavigateCommand { get; }
    // コンストラクタ
    public MainWindowViewModel()
    {

        OpenCommand = new RelayCommand<IFileItem>(Open);
        OpenFolderCommand = new RelayCommand<IFileItem>(OpenFolder);
        MoveFolderCommand = new RelayCommand<string>(MoveFolder);
        MoveParentCommand = new RelayCommand(MoveParent);
        NavigateCommand = new RelayCommand<DirectoryItem>(OnTreeSelected);

        LoadDrives();

        // 初期フォルダー：ピクチャ
        string path = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures);
        Navigate(new FileItem(){Path = path, IsDirectory=true});
    }
    public void Navigate(IFileItem item)
    {
        if (!item.IsDirectory) return;

        if (CurrentPath == item.Path) return;

        CurrentPath = item.Path;

        FileList.Clear();

        foreach (var x in FileService.GetFlieList(item.Path))
        {
            FileList.Add(x);
        }
    }
    private void Open(IFileItem? item)
    {
        if (item == null) return;

        if (item.IsDirectory)
        {
            Navigate(item);
        }
        else
        {
            Process.Start(new ProcessStartInfo
            {
                FileName = item.Path,
                UseShellExecute = true
            });
        }
    }

    private void OpenFolder(IFileItem? item)
    {
        if (item == null) return;

        var dir = item.IsDirectory
            ? item.Path
            : Path.GetDirectoryName(item.Path);

        if (dir != null)
        {
            Process.Start("explorer.exe", dir);
        }
    }
    private void MoveFolder(string path)
    {
        if (File.Exists(path))
            path = Path.GetDirectoryName(path) ?? path;
        if (!Directory.Exists(path)) return;

        Navigate(new FileItem(){Path = path, IsDirectory=true});
    }
    private void MoveParent()
    {
        string root = Path.GetPathRoot(this.CurrentPath) ?? "";
        if ( root.Equals(CurrentPath) ) return;

        var path = Path.GetDirectoryName(this.CurrentPath) ?? "";
        if (!Directory.Exists(path)) return;

        Navigate(new FileItem(){Path = path, IsDirectory=true});
    }
    private void LoadDrives()
    {
        RootDirectories.Clear();

        foreach (var drive in DriveInfo.GetDrives())
        {
            // リムーバブル無視
            if (drive.DriveType == DriveType.Removable)
                continue;

            // 未接続も除外
            if (!drive.IsReady)
                continue;
            

            var child = new DirectoryItem
            {
                Name = drive.Name,
                FullPath = drive.RootDirectory.FullName,
                HasDummy = true,
            };
            child.Children.Add(new DirectoryItem());
            RootDirectories.Add(child);

        }
    }
    private void OnTreeSelected(DirectoryItem? item)
    {
        if (item == null) return;

        if (!item.IsExpanded)
            item.IsExpanded = true;
        
        Navigate(new FileItem(){Path = item.FullPath, IsDirectory=true});
    }
}

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net10.0-windows</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <UseWPF>true</UseWPF>
    <!-- <ApplicationIcon>Assets/App.ico</ApplicationIcon> -->
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="ReactiveProperty.WPF" Version="9.8.0" />
  </ItemGroup>

	<ItemGroup>
		<Resource Include="Assets\**\*.*" />
	</ItemGroup>
  
</Project>