WPFヘルパー:TreeViewSelectedItemBehavior.cs – ツリービューのアイテム選択

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace Maywork.WPF.Helpers;

public static class TreeViewSelectedItemBehavior
{
    public static readonly DependencyProperty SelectedItemChangedCommandProperty =
        DependencyProperty.RegisterAttached(
            "SelectedItemChangedCommand",
            typeof(ICommand),
            typeof(TreeViewSelectedItemBehavior),
            new PropertyMetadata(null, OnChanged));

    public static void SetSelectedItemChangedCommand(DependencyObject obj, ICommand value)
        => obj.SetValue(SelectedItemChangedCommandProperty, value);

    public static ICommand GetSelectedItemChangedCommand(DependencyObject obj)
        => (ICommand)obj.GetValue(SelectedItemChangedCommandProperty);

    private static void OnChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is not TreeView tree) return;

        tree.SelectedItemChanged -= OnSelectedItemChanged;

        if (e.NewValue != null)
        {
            tree.SelectedItemChanged += OnSelectedItemChanged;
        }
    }

    private static void OnSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        if (sender is not TreeView tree) return;

        var cmd = GetSelectedItemChangedCommand(tree);
        if (cmd == null) return;

        if (cmd.CanExecute(e.NewValue))
        {
            cmd.Execute(e.NewValue);
        }
    }
}