推荐使用：

1.配合依赖注入进行配置，利用"reloadOnChange"机制

2.Nuget安装：

Install-Package Microsoft.Extensions.Options

Install-Package Microsoft.Extensions.Configuration 

Install-Package Microsoft.Extensions.Configuration.Json

Install-Package Microsoft.Extensions.Configuration.Binder 

3.在读取配置的时候使用依赖注入Options（下面是读取的即时性：代码执行时配置文件改变了）

IOptions ：不会读到变更的值

IOptionsMonitor ：即时读取变更的值

IOptionsSnapshot :  一次范围内/一个方法（例如：一次HTTP请求）  值保持不变，如果变更了，则在下次操作读取新的值（推荐）

上代码：新建控制台项目：

-- Config.Json

{
  "name": "zhangsan",
  "age": 18,
  "classInfo": {
    "teacher": "Miss Wang",
    "className": "grade one",
    "seat": [2,8] 
  } 
}

-- Demo.cs

    internal class Demo
    {
        private readonly IOptionsSnapshot options;

        public Demo(IOptionsSnapshot options)
        {
            this.options = options;
        }

        public void GetStudentInfo()
        {
            Console.WriteLine(options.Value.ToString());
        }
        public void GetClassInfo()
        {
            Console.WriteLine(options.Value.classInfo.ToString());
        }
    }

-- Program.cs

using DI_ReadConfig;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

ServiceCollection sc=new ServiceCollection();
ConfigurationBuilder configurationBuilder = new ConfigurationBuilder();
configurationBuilder.AddJsonFile("Config.json", true/*防止读取出错*/, true/*文件变更重新加载*/);//加载文件
IConfigurationRoot configurationRoot = configurationBuilder.Build();
sc.AddOptions().Configure(s=> configurationRoot.Bind(s)); // 添加配置绑定
sc.AddScoped();

using (ServiceProvider sp = sc.BuildServiceProvider()) 
{
   Demo demo= sp.GetRequiredService();
   demo.GetStudentInfo();
   demo.GetClassInfo();
}



public class Student
{
    public string Name { get; set; }
    public int Age { get; set; }
    public ClassInfo classInfo { get; set; }

    public override string ToString()
    {
        return $"我是{Name},今年{Age}岁";
    }
}
public class ClassInfo
{
    public string Teacher { get; set; }
    public string ClassName { get; set; }
    public int[] Seat { get; set; }
    public override string ToString()
    {
        return $"老师是{Teacher} 班级：{ClassName} 坐在第{Seat[0]}排第{Seat[1]}列";
    }
}

来看输出：

 如果只想读取班级信息怎么办？

新增类Demo2

internal class Demo2
    {
        private readonly IOptionsSnapshot _options;

        public Demo2(IOptionsSnapshot options)
        {
            this._options = options;
        }

        public void GetClassInfo()
        {
            Console.WriteLine(_options.Value.ToString());
        } 
    }

修改-program

ServiceCollection sc=new ServiceCollection();
sc.AddScoped();---------------------------------------------------增加

ConfigurationBuilder configurationBuilder = new ConfigurationBuilder(); 
configurationBuilder.AddJsonFile("Config.json", true/*防止读取出错*/, true/*文件变更重新加载*/);//加载文件 
IConfigurationRoot configurationRoot = configurationBuilder.Build(); 
sc.AddOptions().Configure(s=> configurationRoot.Bind(s))// 添加配置绑定 
.Configure(c=> configurationRoot.GetSection("ClassInfo").Bind(c)); //绑定班级信息----------------------------------------------------增加 

using (ServiceProvider sp = sc.BuildServiceProvider()) 
{ 
　　Demo2 demo= sp.GetRequiredService();
 demo.GetClassInfo(); 
}

来看输出：

 继续来看看是否会读取最新配置：

新建Winform项目：

--Config.json

复制上面的

--Form1.cs【设计】

--Form1.cs 代码：

public partial class Form1 : Form
    {
       private readonly ServiceCollection sc;
        public Form1()
        {
            InitializeComponent();
            textBox1.Text = "Config.json";
             sc = new ServiceCollection();
            sc.AddScoped();


            ConfigurationBuilder configurationBuilder = new ConfigurationBuilder();
            configurationBuilder.AddJsonFile("Config.json", true/*防止读取出错*/, true/*文件变更重新加载*/);//加载文件
            IConfigurationRoot configurationRoot = configurationBuilder.Build();


            sc.AddOptions().Configure(s => configurationRoot.Bind(s))// 添加配置绑定
                .Configure(c => configurationRoot.GetSection("ClassInfo").Bind(c)); //绑定班级信息 
        }

        private void button1_Click(object sender, EventArgs e)
        {
            using (ServiceProvider sp = sc.BuildServiceProvider())
            {
                Demo2 demo = sp.GetRequiredService();
                textBox2.Text= demo.GetClassInfo();
            }
        }
    }
    internal class Demo2
    {
        private readonly IOptionsSnapshot _options;

        public Demo2(IOptionsSnapshot options)
        {
            this._options = options;
        }

        public string GetClassInfo()
        {
            return _options.Value.ToString();
        }
    }
    public class Student
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public ClassInfo classInfo { get; set; }

        public override string ToString()
        {
            return $"我是{Name},今年{Age}岁";
        }
    }
    public class ClassInfo
    {
        public string Teacher { get; set; }
        public string ClassName { get; set; }
        public int[] Seat { get; set; }
        public override string ToString()
        {
            return $"老师是{Teacher} 班级：{ClassName} 坐在第{Seat[0]}排第{Seat[1]}列";
        }
    }

先点击按钮：查看结果：

 去到Bin下面找到Config.json 用文本文件打开：

把2改成12，点击ctro+S 保存，再去点击按钮试试。

 想试试及时读取和不读取可以在代码中间增加Thread.Sleep(10000) 之类的代码，在程序阻塞时修改文件进行测试验证效果！