Winform保留最近用户登录信息

在这里我只保留了用户账号：

//登录时加载
private void Login_Load(object sender, EventArgs e)
        {
            if (File.Exists("http://www.cnblogs.com/nearuser.txt"))
            {
                StreamReader sr = new StreamReader("http://www.cnblogs.com/nearuser.txt", System.Text.Encoding.UTF8);
                txtUser.Text = sr.ReadLine();
                sr.Close();
            }
        }

//登录成功后写入txt
public void Writetxtfile()
        {
            FileStream fs = null;
            StreamWriter sw = null;
            string str = user.userid;
            try
            {
                fs = new FileStream("http://www.cnblogs.com/nearuser.txt", FileMode.Create);
                sw = new StreamWriter(fs, System.Text.Encoding.Unicode);
                sw.WriteLine(str.ToString());
                sw.Close();
                fs.Close();
            }
            catch (Exception ex)
            {
                sw.Close();
                fs.Close();
            }
        }