如何在startup.cs的Configure方法中使用ConfigurationBinder

Question

asp.net mvc 6 beta5

我尝试使用 config.json 来 activate\disactive 记录

public IConfiguration Configuration { get; set; }

public Startup(IHostingEnvironment env, IApplicationEnvironment appEnv)
         {
            var configurationBuilder = new ConfigurationBuilder(appEnv.ApplicationBasePath)
            .AddJsonFile("config.json")
            .AddEnvironmentVariables();
            Configuration = configurationBuilder.Build();

            DBContext.ConnectionString = Configuration.Get("Data:DefaultConnection:ConnectionString");
        }

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

// Configure is called after ConfigureServices is called.
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerfactory)
        {
            // that line cause NullReferenceException  
            AppSettings settings = ConfigurationBinder.Bind<AppSettings>(Configuration);  
             if (settings.Log.IsActive)
             {
              ................
        }

示例来自 and http://perezgb.com/2015/07/04/aspnet-5-typed-settings-with-the-configurationbinder/
是否有另一种方法可以在 "configure" 方法中获取 AppSettings 的实例？我需要键入的对象。

Answer 1

您可以使用服务定位器这样获取它：

IOptions<AppSettings> settings = app.ApplicationServices.GetService<IOptions<AppSettings>>();
if (settings.Options.whatever)
  {
     ...
  }

我注意到如果您使用 VS 2015 的最终版本创建一个新项目，项目模板不会像以前的项目模板那样包含 AppSettings，不知道为什么。

Answer 2

ConfigureServices 中配置的每个服务都可以由运行时注入 Configure 方法：

public void Configure(IApplicationBuilder app, IOptions<AppSettings> options)
{
    // access options.Options here
}

这个解决方案比直接访问 ServiceProvider 更简洁。