json配置文件示例 

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "Account": {"username": "zhangsan","password":"123"},
  "AllowedHosts": "*"
}

例如读取Account节点数据

方法一

string username = builder.Configuration["Account:username"];
string password = builder.Configuration["Account:password"];

方法二

string username = builder.Configuration.GetSection("Account:username").Value;
string password = builder.Configuration.GetSection("Account:password").Value;

方法三

string username = builder.Configuration.GetValue<string>("Account:username");
string password = builder.Configuration.GetValue<string>("Account:password");

在增加一个数组的节点

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "Account": {
    "username": "zhangsan",
    "password": "123"
  },
  "Port": [1,2,3,4],
  "AllowedHosts": "*"
}

用泛型方法builder.Configuration.GetVaue<T>("key")读取配置的，结果返回null

 对于数组我们只能这样读取

 var Port0 = builder.Configuration.GetValue<int>("Port:0");
 var Port1 = builder.Configuration.GetValue<int>("Port:1");
 var Port2 = builder.Configuration.GetValue<int>("Port:2");
 var Port3 = builder.Configuration.GetValue<int>("Port:3");

因为配置文件都是键值的形式存在，而对于数组而言，下标就是它的键，通过下标找到对应的值 

对于这样太繁琐，我想返回跟配置一样的数组形式 可以这样

var Port=builder.Configuration.GetSection("Port").GetChildren().Select(x => x.Value).ToArray();

运行结果 ，得到我们想要的

 

 方法四

新建一个类，跟配置文件节点名保持一致

public class Account {
        public string username { get; set; }
        public string password { get; set; }
}

找到这个节点绑定到这个类

  Account account = new Account();
  builder.Configuration.Bind("Account", account);

 运行结果

 

 同理

 对于前面读取数组，也能用绑定方式获取

List<int> Port = new List<int>();    
builder.Configuration.Bind("Port", Port);

以上都是在Program.cs中读取，如何在控制器中读取呢

在Program.cs中加入

 builder.Services.Configure<Account>(builder.Configuration.GetSection("Account"));

在控制器中注入

 private readonly IOptionsSnapshot<Account> optAccountSettings

在接口中

 [HttpGet]
 public IActionResult Account()
 {

   var db = _optAccountSettings.Value;
   return Ok(db);
}

 返回结果