{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "Tecent": {
    "Qzone": {
      "Url": "http://i.qq.com",
      "CName": "QQ空间",
      "Age": 15
    },
    "Weixin": {

    }
  
  }
}

    public interface ITecentConfig
    {
        QzoneConfig Qzone { get; set; }
    }

    public class TecentConfig : ITecentConfig
    {
        public QzoneConfig Qzone { get; set; }
    }

    public class QzoneConfig
    {
        public string Url { get; set; }

        public string CName { get; set; }

        public int Age { get; set; }
    }

    public static class ServiceCollectionExtensions
    {
        public static void ConfigureApplicationServices(this IServiceCollection services, IConfiguration configuration)
        {
            ITecentConfig tencentConfig = services.ConfigureStartupConfig<ITecentConfig, TecentConfig>(configuration.GetSection("Tecent"));

            //由于已经通过依赖注入了，并且单例模式，下面通过依赖注入读取配置。
            
        }

        public static TConfig ConfigureStartupConfig<TConfig>(this IServiceCollection services, IConfiguration configuration) 
            where TConfig : class, new()
        {
            if (services == null)
                throw new ArgumentNullException(nameof(services));
            if (configuration == null)
                throw new ArgumentNullException(nameof(configuration));
            var config = new TConfig();
            configuration.Bind(config);
            services.AddSingleton(config);
            //.NET Core DI 为我们提供的实例生命周其包括三种：
            //Transient： 每一次GetService都会创建一个新的实例
            //Scoped：  在同一个Scope内只初始化一个实例 ，可以
            //          理解为（ 每一个request级别只创建一个实例，同一个http request会在一个 scope内）
            //Singleton ：整个应用程序生命周期以内只创建一个实例
            return config;
        }

        public static IConfig ConfigureStartupConfig<IConfig, ConfigImpl>(this IServiceCollection services, IConfiguration configuration)
            where ConfigImpl : class, IConfig, new()
        {
            if (services == null)
                throw new ArgumentNullException(nameof(services));
            if (configuration == null)
                throw new ArgumentNullException(nameof(configuration));
            var config = new ConfigImpl();
            configuration.Bind(config);
            services.AddSingleton(typeof(IConfig), config);
            return config;
        }
    }

    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<CookiePolicyOptions>(options =>
            {
                options.CheckConsentNeeded = context => true;
            });
            services.ConfigureApplicationServices(Configuration);//注册我们自定义的服务

            //注册自定义的模型绑定
            services.AddMvc()
            .AddNewtonsoftJson();
            services.AddRazorPages();
        }
}

    public class HomeController : Controller
    {
        private ITecentConfig _tecentConfig;

        public HomeController(ITecentConfig tecentConfig)
        {
            _tecentConfig = tecentConfig;
        }

        public IActionResult About()
        {
            return Content(string.Format("这个是 About 介绍。{0}: {1}。HashCode：{2}", 
                    _tecentConfig.Qzone.CName, 
                    _tecentConfig.Qzone.Url,
                    _tecentConfig.GetHashCode()
                    )
                );
        }
    }