Program.cs

using System;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form2());
        }
    }
}

public class Form2 : Form
{
    public Form2()
    {
        this.IsMdiContainer = true;

        MenuStrip ms = new MenuStrip();
        ToolStripMenuItem windowMenu = new ToolStripMenuItem("&Test&");

        windowMenu.DropDownItems.Add(new ToolStripMenuItem("&", null, new EventHandler(nothing)));
        windowMenu.DropDownItems.Add(new ToolStripMenuItem("&test", null, new EventHandler(nothing)));
        windowMenu.DropDownItems.Add(new ToolStripMenuItem("test&", null, new EventHandler(nothing)));

        ms.Items.Add(windowMenu);

        this.MainMenuStrip = ms;
        this.Controls.Add(ms);
    }

    void nothing(object sender, EventArgs e)
    {
    }
}