appsetting.josn檔案：

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=db;Trusted_Connection=True;MultipleActiveResultSets=true"
  },
  "Logging": {
    //Debug中最低輸出級別Information
    "Debug": {
      "LogLevel": {
        "Default": "Trace"
      }
    },
    
 
//Console中最低輸出級別Trace
    "Console": {
      "LogLevel": {
        "Default": "Information"
      }
    },
    "LogLevel": {
      "Default": "Trace" //日誌最低級別
    }
  },
  "AllowedHosts": "*"
}

讀取：

public IActionResult Config()
{
    ConfigurationBuilder configurationBuilder = new ConfigurationBuilder();
    
 
//獲取根目錄
    configurationBuilder.SetBasePath(Directory.GetCurrentDirectory()).AddJsonFile("appsettings.json");
    //構建configurationBuilder物件
    var configuration = configurationBuilder.Build();
    //獲取字串
    var conectString = configuration.GetConnectionString("DefaultConnection");
    //獲取AllowedHosts
    var
 
 AllowedHosts = configuration["AllowedHosts"];
    //獲取Loggin下的Default
    var Default = configuration["Logging:Console:LogLevel:Default"];

    return Content(Default);
}

appsetting.josn中的json資料

"Student": [
    {
      "name": "張三",
      "age": "36",
      "hobby": [
        {
          "ballGame": "Basketball"
        },
        {
          "skill": "sing"
        }
      ]
    },
    {
      "name": "李四",
      "age": "23"
    }
  ]

讀取：

 //獲取張三的年齡
var name= configuration["Student:0:age"];

//獲取張三唱歌的愛好
var sing = configuration["Student:0:hobby:1:skill"];