MenuItem

private void 文件ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            MessageBox.Show("打开测试");
            //Close();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //表示 System.Windows.Forms.MenuStrip 或 System.Windows.Forms.ContextMenuStrip 上显示的可选选项。 尽管 System.Windows.Forms.ToolStripMenuItem 替换了早期版本的 System.Windows.Forms.MenuItem 控件并添加了功能；但是也可选择保留 System.Windows.Forms.MenuItem 以备向后兼容和将来使用。
            ToolStripMenuItem ms =(ToolStripMenuItem)menuStrip1.Items[0];//获取菜单项
            foreach (ToolStripItem item in ms.DropDownItems)
            {
                item.Enabled = true;
                item.Font=new Font("楷体",12,FontStyle.Bold);
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            ToolStripMenuItem ms = (ToolStripMenuItem) menuStrip1.Items[0];
            foreach (ToolStripMenuItem item in ms.DropDownItems)
            {
                item.Enabled = false;
            }

        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //创建级联菜单  每一个菜单项都是一个ToolStripMnubItem对象
            ToolStripMenuItem ms =(ToolStripMenuItem)menuStrip1.Items[1];
            ToolStripMenuItem ts1=new ToolStripMenuItem("关闭文件选项");
            //ToolStripMenuItem ts2=new ToolStripMenuItem("关闭文件选项");
            //ToolStripMenuItem ts3=new ToolStripMenuItem("关闭所有选项");
            ToolStripMenuItem[]ts=new ToolStripMenuItem[]
                {
                    new ToolStripMenuItem("关闭文件选项"),
                    new ToolStripMenuItem("关闭所有选项")
                };
            ms.DropDownItems.Add(ts1);
            ms.DropDownItems.AddRange(ts);
        }

MSDN:http://msdn.microsoft.com/zh-cn/library/vstudio/system.windows.forms.menustrip(v=vs.90).aspx

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace _274ContextMenuStrip
{
    public partial class Form1 : Form
    {
        private string address;
        public Form1()
        {
            InitializeComponent();
            address = Environment.CurrentDirectory;//记录地址
        }
        private void 打开新窗体ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form2 fm=new Form2();
            fm.MdiParent = this;
            fm.Show();
            fm.Resize+=new EventHandler(f_Resize);
        }

        void f_Resize(object sender,EventArgs e)
        {
            Form2 fm = (Form2)sender;//将Form2作为对象传进来
            ToolStripMenuItem item = new ToolStripMenuItem();
            for (int i = 0; i < fm.contextMenuStrip1.Items.Count; )
            {
                item.DropDownItems.Add(fm.contextMenuStrip1.Items[i]);//添加鼠标右键
            }
            this.contextMenuStrip2.Items.AddRange(
                    new System.Windows.Forms.ToolStripItem[] { item }
                );
        }
        private void button1_Click(object sender, EventArgs e)
        {
            MessageBox.Show(sender.ToString());//测试验证 sender对象
        }

        private void 退出ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

        private void 关闭所有ToolStripMenuItem_Click(object sender, EventArgs e)
        {
           
        }

        private void 打开ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            openFileDialog1.FileName = "*.jpg";//限定打开文件类型
            openFileDialog1.ShowDialog();//弹出选择对话框
            StreamWriter s=new StreamWriter(address+"\History.ini",true);//初始化新实例
            s.WriteLine(openFileDialog1.FileName);//写入
            s.Flush();//清除流
            s.Close();//关闭流
            ShowWindows(openFileDialog1.FileName);
        }

        private void ShowWindows(string fileName)
        {
            Image p = Image.FromFile(fileName);
            Form f=new Form();
            f.MdiParent = this;
            f.BackgroundImage = p;
            f.Show();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.IsMdiContainer = true;
            
            文件ToolStripMenuItem.DropDownItems[1].Image = imageList1.Images[0];

            using (StreamReader sr = new StreamReader(address + "\History.ini"))//创建流读取器对象
            {
                int i = 文件ToolStripMenuItem.DropDownItems.Count - 2;//得到菜单项索引
                while (sr.Peek() >= 0)//循环读取流中的文本
                {
                    ToolStripMenuItem menuItem = new ToolStripMenuItem(sr.ReadLine());//创建菜单项对象
                    this.文件ToolStripMenuItem.DropDownItems.Insert(i, menuItem);//向菜单中添加新项
                    i++;//增加索引位置
                    menuItem.Click += new EventHandler(menuItem_Click);//添加单击事件
                }
            }
        }

        private void menuItem_Click(object sender, EventArgs e)
        {
            ToolStripMenuItem menu = (ToolStripMenuItem) sender;
            ShowWindows(menu.Text);
        }

        private void acToolStripMenuItem_Click(object sender, EventArgs e)
        {
            
        }

      
    }
}