ASP.NET Core 后我们的配置变得更加轻量级了，在ASP.NET Core中，配置模型得到了显著的扩展和增强，应用程序配置可以存储在多环境变量配置中，appsettings.json用户机密等 并可以通过应用程序中的相同界面轻松访问，除此之外，ASP.NET中的新配置系统允许使用Options的强类型设置。

强类型Options

在ASP.NET Core中没有AppSettings["Key"]默认方法，那么推荐的是创建强类型的配置类，去绑定配置项。

public class MyOptions { public string Name { get; set; } public string Url { get; set; } }

然后我们在appsettings.json中添加如下内容：

{ "MyOptions": { "Name": "TestName", "Url": "TestUrl" } } 配置绑定到类

ConfigureServices方法进行配置以绑定到类

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

MyOptions只需将IOptions<>类的实例注入控制器中，，然后通过Value属性获取Myoptions：

public class WeatherForecastController : ControllerBase { private readonly MyOptions _options; public WeatherForecastController(IOptions<MyOptions> options) { _options = options.Value; } [HttpGet] public OkObjectResult Get() { return Ok(string.Format("Name:{0},Url:{1}", _options.Name,_options.Url)); } } Configure 委托配置 //基础注册方式 services.Configure<MyOptions>(o => { o.Url = "MyOptions"; o.Name = "Name111"; }); //指定具体名称 services.Configure<MyOptions>("Option", o => { o.Url = "MyOptions"; o.Name = "Name111"; }) ; //配置所有实例 services.ConfigureAll<MyOptions>(options =>{ options.Name = "Name1"; options.Url = "Url1";}); 通过配置文件配置 // 使用配置文件来注册实例 services.Configure<MyOptions>(Configuration.GetSection("MyOptions")); // 指定具体名称 services.Configure<MyOptions>("Option", Configuration.GetSection("MyOptions")); PostConfigure

PostConfigure会在Configure注册完之后再进行注册

services.PostConfigure<MyOptions>(o => o.Name = "Name1"); services.PostConfigure<MyOptions>("Option", o => o.Name = "Name1"); services.PostConfigureAll<MyOptions>(o => o.Name = "Name1"); 源码解析

IConfigureOptions接口

public interface IConfigureOptions<in TOptions> where TOptions : class { void Configure(TOptions options); }

Configure为方便使用IConfigureOptions注册单例ConfigureNamedOptions

public static IServiceCollection Configure<TOptions>(this IServiceCollection services, string name, Action<TOptions> configureOptions) where TOptions : class { if (services == null) { throw new ArgumentNullException(nameof(services)); } if (configureOptions == null) { throw new ArgumentNullException(nameof(configureOptions)); } services.AddOptions(); services.AddSingleton<IConfigureOptions<TOptions>>(new ConfigureNamedOptions<TOptions>(name, configureOptions)); return services; }

上面代码IConfigureOptions实现了ConfigureNamedOptions，那我们再来看看内部源码
ConfigureNamedOptions 其实就是把我们注册的Action包装成统一的Configure方法，以方便后续创建Options实例时，进行初始化。

public class ConfigureNamedOptions<TOptions> : IConfigureNamedOptions<TOptions> where TOptions : class { public ConfigureNamedOptions(string name, Action<TOptions> action) { Name = name; Action = action; } public string Name { get; } public Action<TOptions> Action { get; } public virtual void Configure(string name, TOptions options) { if (options == null) { throw new ArgumentNullException(nameof(options)); } // Null name is used to configure all named options. if (Name == null || name == Name) { Action?.Invoke(options); } } public void Configure(TOptions options) => Configure(Options.DefaultName, options); }

在 services.Configure(Configuration.GetSection("MyOptions")); 我们不指定具体名称的时候默认是如下代码片段

public virtual void Configure(string name, TOptions options) { if (options == null) { throw new ArgumentNullException(nameof(options)); } // Null name is used to configure all named options. if (Name == null || name == Name) { Action?.Invoke(options); } } public void Configure(TOptions options) => Configure(Options.DefaultName, options);

默认使用的是Options.DefaultName

AddOptions默认方法默认为我们注册了一些核心的类

public static IServiceCollection AddOptions(this IServiceCollection services) { if (services == null) { throw new ArgumentNullException(nameof(services)); } services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptions<>), typeof(OptionsManager<>))); services.TryAdd(ServiceDescriptor.Scoped(typeof(IOptionsSnapshot<>), typeof(OptionsManager<>))); services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitor<>), typeof(OptionsMonitor<>))); services.TryAdd(ServiceDescriptor.Transient(typeof(IOptionsFactory<>), typeof(OptionsFactory<>))); services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitorCache<>), typeof(OptionsCache<>))); return services; }

ASP.NET Core 选项模式源码学习Options Configure（一）