.Net Core 读取配置文件的几种方式（Configuration）

配置 appsettings.json 信息

{ 
  "AppSettings": {
    "IsDebug": true,
    "Version": "1.0.0",
    "Name": "文哥" 
  }
}

创建 一个配置对应类 AppSettingsOptions.cs

    public class AppSettingsOptions
    {
        public bool IsDebug { get; set; }
        public string Name { get; set; } 
        public string Version { get; set; }
    }

依赖注入 IConfiguration 读取 appsettings.json 信息

• 构造函数注入方式

          private readonly IConfiguration _configuration;
          public DemoController(IConfiguration configuration)
          {
              _configuration = configuration;
          }

• 参数注入方式 [FromServices]

          [HttpGet]
          public string Get([FromServices] IConfiguration configuration)
          { 
              var data = App.Configuration.GetSection("AppSettings").Get<AppSettingsOptions>();//对象 
              var name = configuration["AppSettings:Name"]; //文哥 
              var isDebug = configuration.GetValue<bool>("AppSettings:IsDebug"); // true 
              var version = configuration.GetSection("AppSettings").GetSection("Version").Value; // 1.0.0 
              return version;
          }

选项模式读取 appsettings.json 信息

1. 需在Startup.cs注册

           public void ConfigureServices(IServiceCollection services)
           { 
               services.Configure<AppSettingsOptions>(Configuration.GetSection("AppSettings"));
           }

2. 读取 AppSettingsOptions信息

   //通过依赖注入以下实例读取：
   IOptions<TOptions> //单例，不支持数据变化(重启更新)，性能高
   IOptionsMonitor<TOptions> //单例，实时变更（侦听器OnChange）
   IOptionsSnapshot<TOptions>// 作用域注册，单次请求内不变

3. 依赖注入

           //构造函数注入
           private readonly IOptionsMonitor<AppSettingsOptions> _settings;
           public DemoController(IOptionsMonitor<AppSettingsOptions> settings)
           {
               _settings= settings;
           }
           //参数注入方式 [FromServices]
           [HttpGet]
           public string Get([FromServices] IOptionsMonitor<AppSettingsOptions> settings)
           {
               return JsonSerializer.Serialize(settings.CurrentValue) ;
           }