private void button1_Click(object sender, EventArgs e)        {            string aa = this.richTextBox1.Text.Trim();            StreamWriter sfile = new StreamWriter("E://123.txt");//写入到123.txt文件中            sfile.Write(aa);            sfile.Close();            StreamReader ss = new StreamReader("E://123.txt");//读取文件123.txt中的内容            this.richTextBox2.Text = ss.ReadLine();            ss.Close();        }