WebClient client = new WebClient();
byte[] buffer = client.DownloadData("http://xxx.xxx.xxx.xx:8888/announcement.txt");
string res = Encoding.GetEncoding("GB2312").GetString(buffer);
//string res = System.Text.ASCIIEncoding.ASCII.GetString(buffer);
rtxtNotice.Text = res;

private void btSave_Click(object sender, EventArgs e)  //保存txt文件
{
                saveFileDialog1.Filter = ("文本文件(*.txt)|*.txt");  //創(chuàng)建一個(gè)篩選器
                if (saveFileDialog1.ShowDialog() == DialogResult.OK)  //判斷按下的是保存還是取消
                {
                    string path = saveFileDialog1.FileName;  //獲得文件名和路徑
                    using (StreamWriter sw = new StreamWriter(path, false))  //保存文件到指定路徑
                    {
                        sw.WriteLine(txtNote.Text);
                    }
}
 

private void btOpen_Click(object sender, EventArgs e)  //打開txt文件
{
            openFileDialog1.Filter = ("文本文件(*.txt)|*.txt");  //創(chuàng)建一個(gè)篩選器
            if (openFileDialog1.ShowDialog() == DialogResult.OK)  //判斷按下的是打開還是取消
            {
                string path = openFileDialog1.FileName;  //獲得文件名和路徑
                using (StreamReader sr = new StreamReader(path, Encoding.UTF8))  //打開文件
                {
                    txtNote.Text = sr.ReadToEnd();
                }
            }
}