C# 实现简易记事本程序

  private void 新建ToolStripMenuItem1_Click(object sender, EventArgs e)
        {
            Form1 f1 = new Form1();
            f1.Name = "记事本";
            f1.Show();
            
        }

        private void 打开ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                FileStream fs = new FileStream(openFileDialog1.FileName, FileMode.Open, FileAccess.Read);
                string a=Path.GetExtension(openFileDialog1.FileName);
                if (a != ".txt")
                {
                    MessageBox.Show("请选择正确格式的文件");
                }
                else
                {
                    StreamReader sr = new StreamReader(fs);
                    richTextBox1.Text = sr.ReadToEnd();
                    sr.Close();
                    fs.Close();
                }
            }
            else
                MessageBox.Show("您已取消读取");
        }

        private void 保存ToolStripMenuItem_Click(object sender, EventArgs e)
        {
             SaveFileDialog sfd = new SaveFileDialog();
            sfd.Title = "请选择保存文件路径";
            sfd.Filter = "文本文件|*.txt|所有文件|*.*";

           
            if (sfd.ShowDialog()==DialogResult.OK)
            {
                FileStream fs = new FileStream(sfd.FileName, FileMode.Create, FileAccess.Write);
                StreamWriter sw = new StreamWriter(fs);
                string[] lines = richTextBox1.Lines;
                for (int i = 0; i < lines.Length; i++)
                {
                    sw.WriteLine(lines[i]);
                }

                sw.Close();
                fs.Close();
            }
                
         
        
        }

        private void 退出ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Close();
        }