C# winform 使用json文件记录用户名、密码

1.在NuGet安装Newtonsoft.Json（这里只用到解码）；

2.窗体设计

3.代码

using System.IO;
//using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

        private void UserLogin_Load(object sender, EventArgs e)
        {
            ReadJson();//读取配置文件        
        }
        private void ReadJson()
        {//读取配置文件
            string jsonPath = Application.StartupPath + @"userInfo.json";
            if (File.Exists(jsonPath))
            {
                try
                {
                    string jsonStr = File.ReadAllText(jsonPath);
                    JObject jsonObj = JObject.Parse(jsonStr);
                    if (jsonObj != null)
                    {//读取用户信息
                        if (jsonObj["id"] != null)
                        {
                            switch (jsonObj["id"].ToString())
                            {//是否记住用户信息
                                case "0"://不记住登陆信息
                                    RdbNotSave.Checked = true;
                                    break;
                                case "1"://记住账号
                                    RdbSaveUserName.Checked = true;
                                    break;
                                case "2"://记住账号和密码
                                    RdbSaveBoth.Checked = true;
                                    break;
                                default:
                                    RdbNotSave.Checked = false;
                                    RdbSaveUserName.Checked = false;
                                    RdbSaveBoth.Checked = false;
                                    break;
                            }
                        }
                        if (jsonObj["userName"] != null)
                        {
                            TxbUsername.Text = jsonObj["userName"].ToString();
                        }
                        if (jsonObj["passWord"] != null)
                        {
                            TxbPassword.Text = jsonObj["passWord"].ToString();
                        }
                    }
                }
                catch
                {
                }
            }
        }
        private void WriteJson(string id, string userName, string passWord)
        {//写入配置文件
            string jsonPath = Application.StartupPath + @"userInfo.json";
            string jsonStr = "{"id":"" + id + "","userName":"" + userName + "","passWord":"" + passWord + ""}";
            File.WriteAllText(jsonPath, jsonStr);
        }
        private void BtnLogin_Click(object sender, EventArgs e)
        {//登录按钮
            //连接数据库进行登录检测，这里操作数据库代码省略if (/**/)
            {//登成功
               //判断记录状态
               if (RdbNotSave.Checked)
               {//不记住登陆信息
                  WriteJson("0", "", "");
               }
               else if (RdbSaveUserName.Checked)
               {//记住账号
                  WriteJson("1", TxbUsername.Text.Trim(), "");
               }
               else if (RdbSaveBoth.Checked)
               {//记住账号和密码
                  WriteJson("2", TxbUsername.Text.Trim(), TxbPassword.Text.Trim());
               }
            }
        }

        private void BtnCancel_Click(object sender, EventArgs e)
        {//退出按钮
            Environment.Exit(0);//退出软件
        }

 4：josn文件内容

{"id":"2","userName":"a","passWord":"2"}