[Visual C# 2017][WPF] WpfBindableListBoxSample

Commands\DelegateCommand.cs

using System;
using System.Windows.Input;

namespace WpfBindableListBoxSample.Commands
{
    public class DelegateCommand : ICommand
    {
        private Action _execute;
        private Func<bool> _canExecute;

        public DelegateCommand(Action execute, Func<bool> canExecute)
        {
            _execute = execute;
            _canExecute = canExecute;
        }

        public void Execute(object parameter)
        {
            _execute();
        }

        public bool CanExecute(object parameter)
        {
            return _canExecute();
        }

        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }
    }
}

Controls\BindableListBox.cs

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

using System.Collections;  // IList

namespace WpfBindableListBoxSample.Controls
{
    public class BindableListBox : ListBox
    {
        public new static readonly DependencyProperty SelectedItemsProperty =
            DependencyProperty.Register(
            nameof(SelectedItems), typeof(IList),
            typeof(BindableListBox),
            new FrameworkPropertyMetadata(null,
                FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));

        public new IList SelectedItems
        {
            get { return (IList)this.GetValue(SelectedItemsProperty); }
            set { this.SetValue(SelectedItemsProperty, value); }
        }

        protected override void OnSelectionChanged(SelectionChangedEventArgs e)
        {
            base.OnSelectionChanged(e);

            this.SelectedItems = base.SelectedItems;
        }
    }
}

MainWindow.xaml

<Window x:Class="WpfBindableListBoxSample.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:WpfBindableListBoxSample"
        mc:Ignorable="d"
        xmlns:vm="clr-namespace:WpfBindableListBoxSample.ViewModels"
        xmlns:ctrl="clr-namespace:WpfBindableListBoxSample.Controls"
        Title="MainWindow" Height="350" Width="525">

    <Window.DataContext>
        <vm:MainViewModel />
    </Window.DataContext>

    <Window.InputBindings>
        <KeyBinding Gesture="Enter" 
            Command="{Binding Path=ShowSelectedItemsCommand}" />
    </Window.InputBindings>

    <Grid>
        <ctrl:BindableListBox SelectionMode="Extended" 
            ItemsSource="{Binding Path=Items}" 
            SelectedItems="{Binding SelectedItems}">
            <ctrl:BindableListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock>
                        <TextBlock.Text>
                            <MultiBinding StringFormat="{}{0},{1}">
                                <Binding Path="Name" />
                                <Binding Path="Age" />
                            </MultiBinding>
                        </TextBlock.Text>
                    </TextBlock>
                </DataTemplate>
            </ctrl:BindableListBox.ItemTemplate>
        </ctrl:BindableListBox>
    </Grid>
</Window>

MainWindow.xaml.cs

using System.Windows;

namespace WpfBindableListBoxSample
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }
}

Models\Person.cs

namespace WpfBindableListBoxSample.Models
{
    public class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }

        public Person(string name, int age)
        {
            this.Name = name;
            this.Age = age;
        }
    }
}

ViewModels\MainViewModel.cs

using System;
using System.Windows;

using System.ComponentModel;  // INotifyPropertyChanged
using System.Collections.ObjectModel;  // ObservableCollection
using System.Collections;  // IList

using WpfBindableListBoxSample.Commands;
using WpfBindableListBoxSample.Models;

namespace WpfBindableListBoxSample.ViewModels
{
    public class MainViewModel : INotifyPropertyChanged
    {
        // ---------------------------------------------------------------------
        // プロパティ - リスト

        private ObservableCollection<Person> _items;
        public ObservableCollection<Person> Items
        {
            get { return _items; }
            set
            {
                _items = value;
                this.OnPropertyChanged(nameof(Items));
            }
        }

        public IList SelectedItems { get; set; }

        // ---------------------------------------------------------------------
        // プロパティ - コマンド

        private DelegateCommand _showSelectedItemsCommand;
        public DelegateCommand ShowSelectedItemsCommand
        {
            get
            {
                if (_showSelectedItemsCommand == null)
                {
                    _showSelectedItemsCommand = new DelegateCommand(
                        () => this.DoShowSelectedItems(),
                        () => this.SelectedItems != null
                     );
                }
                return _showSelectedItemsCommand;
            }
        }

        private void DoShowSelectedItems()
        {
            string message = "";
            foreach (Person item in this.SelectedItems)
            {
                message += item.Name + "," + item.Age + Environment.NewLine;
            }
            MessageBox.Show(message);
        }

        // ---------------------------------------------------------------------
        // コンストラクタ

        public MainViewModel()
        {
            // 動作テスト用データ
            this.Items = new ObservableCollection<Person>();
            this.Items.Add(new Person("太郎", 39));
            this.Items.Add(new Person("花子", 34));
            this.Items.Add(new Person("次郎", 28));
            this.Items.Add(new Person("良子", 22));
            this.Items.Add(new Person("三郎", 15));
        }

        // ---------------------------------------------------------------------
        // インターフェースの実装 - INotifyPropertyChanged

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(string name)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
        }
    }
}