记住密码：

         Dictionary<string, User> users = new Dictionary<string, User>();//记住密码private void Password(){//执行目录下面创建data.bin文件,用来存放账号密码FileStream fs = new FileStream("data.bin", FileMode.Create);BinaryFormatter bf = new BinaryFormatter();//账号自动保存user.LoginID = txt_UserID.Text.Trim();//如果勾选了记住密码，就保存密码，否则保存空值if (CB_Rpwd.Checked){user.Pwd = txt_Password.Text.Trim();}else{user.Pwd = "";}if (users.ContainsKey(user.LoginID)){users.Remove(user.LoginID);}users.Add(user.LoginID, user);bf.Serialize(fs, users);fs.Close();this.Dispose();}

输入账号自动带出密码：

         private void txt_UserID_SelectedIndexChanged(object sender, EventArgs e){FileStream fs = new FileStream("data.bin", FileMode.OpenOrCreate);if (fs.Length > 0){BinaryFormatter bf = new BinaryFormatter();users = bf.Deserialize(fs) as Dictionary<string, User>;for (int i = 0; i < users.Count; i++){if (txt_UserID.Text.Trim() != ""){if (users.ContainsKey(txt_UserID.Text.Trim()) && users[txt_UserID.Text].Pwd != ""){txt_Password.Text = users[txt_UserID.Text].Pwd;CB_Rpwd.Checked = true;}else{txt_Password.Text = "";CB_Rpwd.Checked = false;}}}}fs.Close();}

load函数里面要加载data.bin里的user的下拉

  private void Frm_Login_Load(object sender, EventArgs e){FileStream fs = new FileStream("data.bin", FileMode.OpenOrCreate);if (fs.Length > 0){BinaryFormatter bf = new BinaryFormatter();users = bf.Deserialize(fs) as Dictionary<string, User>;foreach (User user in users.Values){txt_UserID.Properties.Items.Add(user.LoginID);}//for (int i = 0; i < users.Count; i++)//{//    if (txt_UserID.Text.Trim() != "")//    {//        if (users.ContainsKey(txt_UserID.Text.Trim()))//        {//            txt_Password.Text = users[txt_UserID.Text].Pwd;//            CB_Rpwd.Checked = true;//        }//    }//}}fs.Close();}