XAMLを使わないWPF入門23「メインメニューの最小サンプル」

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

  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>net8.0-windows</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <UseWPF>true</UseWPF>
  </PropertyGroup>

</Project>

using System;
using System.Windows;

namespace NoXAML23Mainmenu;

public class App : Application
{
    [STAThread]
    public static void Main(string[] args)
    {
        var app = new App();
        app.Run();
    }

    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);
        var win = new MainWindow();
        win.Show();
    }
}

using System.Windows;

[assembly:ThemeInfo(
    ResourceDictionaryLocation.None,            //where theme specific resource dictionaries are located
                                                //(used if a resource is not found in the page,
                                                // or application resource dictionaries)
    ResourceDictionaryLocation.SourceAssembly   //where the generic resource dictionary is located
                                                //(used if a resource is not found in the page,
                                                // app, or any theme specific resource dictionaries)
)]

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

namespace NoXAML23Mainmenu;

public class MainWindow : Window
{
    public MainWindow()
    {
        Title = "NoXAML Menu Sample";
        Width = 400;
        Height = 200;

        // メニュー生成
        var menu = new Menu();

        // 「ファイル」メニュー
        var fileMenu = new MenuItem { Header = "_ファイル" };

        // 「開く」
        var openItem = new MenuItem { Header = "_開く" };
        openItem.Click += (s, e) => MessageBox.Show("開くが選択されました");

        // 「終了」
        var exitItem = new MenuItem { Header = "_終了" };
        exitItem.Click += (s, e) => Close();

        // サブメニュー追加
        fileMenu.Items.Add(openItem);
        fileMenu.Items.Add(new Separator());
        fileMenu.Items.Add(exitItem);

        // メニューにファイルメニュー追加
        menu.Items.Add(fileMenu);

        // メニューをウィンドウに配置
        var dock = new DockPanel();
        DockPanel.SetDock(menu, Dock.Top);
        dock.Children.Add(menu);

        Content = dock;
    }
}