C#のWPFでListViewの選択項目とテキストボックスをバインドする。

using System.ComponentModel;
using Reactive.Bindings;

namespace CollectionBinding3;
public class FileEntity : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler? PropertyChanged;
    protected virtual void OnPropertyChanged(string name) =>
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    
    public ReactiveProperty<string> Name { get; set; } = new("");
    public ReactiveProperty<string> FullName { get; set; } = new("");
    public ReactiveProperty<string> Comment {get; set;} = new("");
 }

<Window x:Class="CollectionBinding3.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:i="clr-namespace:Microsoft.Xaml.Behaviors;assembly=Microsoft.Xaml.Behaviors"
        xmlns:interactivity="clr-namespace:Reactive.Bindings.Interactivity;assembly=ReactiveProperty.WPF"
        xmlns:local="clr-namespace:CollectionBinding3"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.DataContext>
        <local:MainWindowViewModel />
    </Window.DataContext>
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Loaded">
            <interactivity:EventToReactiveCommand Command="{Binding WindowLoadedCommand}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <ListView
            x:Name="FilesListView"
            Grid.Column="0"
            IsSynchronizedWithCurrentItem="True" 
            ItemsSource="{Binding Files}"
            SelectedIndex="{Binding FilesListViewSelectedIndex.Value}">
            <ListView.Resources>
                <Style x:Key="listviewHeaderStyle" TargetType="GridViewColumnHeader">
                    <Setter Property="HorizontalContentAlignment" Value="Stretch" />
                </Style>
            </ListView.Resources>
            <ListView.View>
                <GridView ColumnHeaderContainerStyle="{StaticResource listviewHeaderStyle}">
                    <GridViewColumn Width="200" Header="名前">
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                    <TextBlock Width="Auto" TextAlignment="Left" Text="{Binding Name.Value}" />
                                </StackPanel>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                    <GridViewColumn Width="300" Header="コメント">
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                    <TextBlock Width="Auto" TextAlignment="Left" Text="{Binding Comment.Value}" />
                                </StackPanel>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                </GridView>
            </ListView.View>
        </ListView>
        <WrapPanel
            Grid.Column="1">
            <Label>コメント</Label>
            <TextBox
                Width="200"
                Text="{Binding Files/Comment.Value}"
                />
        </WrapPanel>
    </Grid>
</Window>

using System.ComponentModel;
using Reactive.Bindings;

using System.Diagnostics;
using System.IO;

namespace CollectionBinding3;

public class MainWindowViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler? PropertyChanged;
    protected virtual void OnPropertyChanged(string name) =>
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    public ReactiveCommand<EventArgs> WindowLoadedCommand { get; }
    public ReactiveCollection<FileEntity> Files { get; set; } = [];
    public ReactiveProperty<int> FilesListViewSelectedIndex { get; set; } = new();
    public MainWindowViewModel()
    {
        WindowLoadedCommand = new ReactiveCommand<EventArgs>()
            .WithSubscribe(e =>
            {
                int i = 0;
                string targetDir = @"H:\csharp\dotnet8\wpf\CollectionBinding3";
                foreach(var fullname in Directory.EnumerateFileSystemEntries(targetDir))
                {
                    var comment = new ReactiveProperty<string>($"{i++}");
                    comment.Subscribe(e =>
                    {
                        int i = FilesListViewSelectedIndex.Value;
                        if (i < 0) return;
                        if (Files.Any() == false) return;
                        string fullname = Files[i].FullName.Value;
                        string comment = Files[i].Comment.Value;
                        if (e != comment) return;
                        Debug.Print($"{fullname}のコメント{comment}");
                    });
                    Files.AddOnScheduler(
                        new FileEntity()
                        {
                            Name = new(Path.GetFileName(fullname)),
                            FullName = new(fullname),
                            Comment = comment,
                        }
                    );
                }
            }
        );
        FilesListViewSelectedIndex
            .Subscribe(e=>
            {
                // リストビューの選択が変更されると実行される。
                int index = e;
                Debug.Print($"選択されたインデックス:{index}");
            }
        );
    }
}