C#第十周任务之最后一项之创建一个如下的窗体，并在窗体上放置一个菜单、一个工具栏控件。菜单内容如第二个图所示。工具栏上有两个按钮，分别对应“打开文本文件”、“保存文本文件”。菜单和工具栏具体功能实现可

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.IO;using System.Windows.Forms;namespace WindowsFormsApplication9{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        private void toolStripComboBox1_Click(object sender, EventArgs e)        {        }        private void toolStripButton1_Click(object sender, EventArgs e)        {            this.saveFileDialog1.Filter = "*.txt|*.txt";              this.saveFileDialog1.ShowDialog();             string file = this.saveFileDialog1.FileName;              if (string.IsNullOrEmpty(file)) return;              //以下为写字符到文本文件，需要添加System.IO引用               //创建一个文件流               FileStream fs = new FileStream(file, FileMode.OpenOrCreate,                  FileAccess.Write);             //创建一个StreamWriter对象              StreamWriter sw = new StreamWriter(fs);              sw.Write(this.textBox1.Text);              //释放StreamWriter对象,文件流对象              sw.Dispose();              fs.Dispose();          }        private void toolStripButton2_Click(object sender, EventArgs e)        {            this.openFileDialog1.Filter = "*.txt|*.txt";            this.openFileDialog1.ShowDialog();            string file = this.openFileDialog1.FileName;            if (string.IsNullOrEmpty(file)) return;            //以下为写字符到文本文件，需要添加System.IO引用            //创建一个文件流            FileStream fs = new FileStream(file, FileMode.Open,                FileAccess.Read);            //创建一个StreamWriter对象            StreamReader sr = new StreamReader(fs);            this.textBox1.Text = sr.ReadToEnd();            //释放StreamWriter对象,文件流对象            sr.Dispose();            fs.Dispose();        }        private void textBox1_TextChanged(object sender, EventArgs e)        {        }    }}