C# 文件流基本操作方法

private void button1_Click(object sender, EventArgs e)        {            FileStream fs = new FileStream("123.txt", FileMode.Append);            StreamWriter ws = new StreamWriter(fs);            ws.WriteLine(this.txtbox.Text = DateTime.Now.ToString()+"  " + "写入成功");            ws.Close();            fs.Close();        }        private void button2_Click(object sender, EventArgs e)        {            FileStream fs = new FileStream("123.txt", FileMode.Open);                       StreamReader ws = new StreamReader(fs);            this.txtbox.Text = ws.ReadToEnd();            ws.Close();            fs.Close();        }