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("Account:username");
string password = builder.Configuration.GetValue("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("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("Port:0");var Port1 = builder.Configuration.GetValue("Port:1");var Port2 = builder.Configuration.GetValue("Port:2");var Port3 = builder.Configuration.GetValue("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 Port = new List();    
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(builder.Configuration.GetSection("Account"));

在控制器中注入

 private readonly IOptionsSnapshot optAccountSettings

在接口中

 [HttpGet]public IActionResult Account(){var db = _optAccountSettings.Value;return Ok(db);
}

 返回结果