ボタンを自作できる MessageBox

Dialog.usage.cs

private void button_Click_1(object sender, RoutedEventArgs e)
{
    var selection = new Dialog().show("うぃんどうたいとる", "ああああああい\nいいいいいいいいい\nうううううううううううう\nnagaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaai-text\n１２３", new List<string>
    {
        "ボタン01", "ボタン02", "ボタン03",
        "ボタン04", "ポタン05", "ボタン06",
        "ボタン07", "ボタン08", "ボタン09",
        "ボタン10", "ボタン11", "ボタン12",
    });
    Console.WriteLine(selection);
}

Dialog.xaml

<Window x:Class="liblib.Dialog"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
        xmlns:local="clr-namespace:liblib"
        mc:Ignorable="d"
        ResizeMode="NoResize"
        SizeToContent="WidthAndHeight"
        Title="{Binding title}"
        FontSize="13"
        MaxWidth="640"
        MaxHeight="640"
        d:DesignHeight="200" d:DesignWidth="200">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>

        <TextBlock Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Center" TextWrapping="Wrap" Text="{Binding message}" Margin="30 40 30 30"/>

        <Border Grid.Row="1" Background="Cornsilk">
            <ItemsControl HorizontalAlignment="Center" VerticalAlignment="Center" ItemsSource="{Binding buttons}" Margin="20 5" Button.Click="onbuttonclick" AlternationCount="999">
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <WrapPanel />
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <Button Margin="10" Padding="20 4" Background="#E0E0E0" Content="{Binding}" Tag="{Binding RelativeSource={RelativeSource Mode=TemplatedParent},Path=(ItemsControl.AlternationIndex)}" />
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </Border>
    </Grid>
</Window>

Dialog.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;

namespace liblib
{
    /// <summary>
    /// Dialog.xaml の相互作用ロジック
    /// </summary>
    public partial class Dialog : Window
    {
        private class BindingData : NotifyHelper
        {
            private string _title = "";
            public string title
            {
                get { return _title; }
                set
                {
                    this._title = value;
                    this.notifyPropertyChange(nameof(title));
                }
            }

            private string _message = "";
            public string message
            {
                get { return _message; }
                set
                {
                    this._message = value;
                    this.notifyPropertyChange(nameof(message));
                }
            }

            private List<string> _buttons = new List<string>();
            public List<string> buttons
            {
                get { return _buttons; }
                set
                {
                    this._buttons = value;
                    this.notifyPropertyChange(nameof(buttons));
                }
            }
        }

        private int select { get; set; } = -1;

        public Dialog()
        {
            InitializeComponent();
        }

        public int show(string title, string message, IEnumerable<string> selections)
        {
            var buttons = selections.ToList();

            if(buttons.Count > 16)
            {
                throw new ArgumentOutOfRangeException("Too many buttons.");
            }

            this.DataContext = new BindingData
            {
                title = title,
                message = message,
                buttons = selections.ToList(),
            };

            base.ShowDialog();

            return this.select;
        }

        private void onbuttonclick(object sender, RoutedEventArgs e)
        {
            var button = (Button)e.OriginalSource;
            var index = (int)button.Tag;
            this.select = index;

            this.Close();
        }

        public new void Show()
        {
            throw new NotSupportedException("Please use 'show' method.");
        }

        public new void ShowDialog()
        {
            throw new NotSupportedException("Please use 'show' method.");
        }
    }
}