public class UserOptions
{
    private string instanceId;
    private static int index = 0;
    public UserOptions()
    {
        instanceId = (++index).ToString("00");
        Console.WriteLine($"Create UserOptions Instance:{instanceId}");
    }
    public string Name { get; set; }
    public int Age { get; set; }
    public override string ToString() => $"Name:{Name} Age:{Age} Instance:{instanceId} ";
}
public class UserOptions2
{
    public string Name { get; set; }
    public int Age { get; set; }
    public override string ToString() => $" Name:{Name} Age:{Age}";
}

{
  "UserOption": {
    "Name": "ConfigName-zhangsan",
    "Age": 666
  }
}

services = new ServiceCollection();
var configBuilder = new ConfigurationBuilder().AddInMemoryCollection().AddJsonFile("myconfig.json", true, true);
var iconfiguration = configBuilder.Build();
services.AddSingleton<IConfiguration>(iconfiguration);

services.Configure<UserOptions>(x => { x.Name = "張三"; x.Age = new Random().Next(1, 10000); });
services.AddOptions<UserOptions2>().Configure<IConfiguration>((x, config) => { x.Name = config["UserOption:Name"]; x.Age = 100; }); ;
services.PostConfigure<UserOptions>(x => { x.Name = x.Name + "Post"; x.Age = x.Age; });
services.Configure<UserOptions>("default", x => { x.Name = "Default-張三"; x.Age = new Random().Next(1, 10000); });
services.Configure<UserOptions>("config", configuration.GetSection("UserOption"));
using (var provider = services.BuildServiceProvider())
{
    using (var scope1 = provider.CreateScope())
    {
        PrintOptions(scope1, "Scope1");
    }

    //修改配置文件
    Console.WriteLine(string.Empty);
    Console.WriteLine("修改配置文件");
    var filePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "myconfig.json");
    File.WriteAllText(filePath, "{\"UserOption\": { \"Name\": \"ConfigName-lisi\", \"Age\": 777}}");
    //配置文件的change回調(diào)事件需要一定時間執(zhí)行
    Thread.Sleep(300);
    Console.WriteLine(string.Empty);

    using (var scope2 = provider.CreateScope())
    {
        PrintOptions(scope2, "Scope2");
    }

    Console.WriteLine(string.Empty);

    using (var scope3 = provider.CreateScope())
    {
        PrintOptions(scope3, "Scope3");
    }
}

static void PrintOptions(IServiceScope scope, string scopeName)
{
    var options1 = scope.ServiceProvider.GetService<IOptions<UserOptions>>();
    Console.WriteLine($"手動注入讀取,IOptions,{scopeName}-----{ options1.Value}");

    var options2 = scope.ServiceProvider.GetService<IOptionsSnapshot<UserOptions>>();
    Console.WriteLine($"配置文件讀取,IOptionsSnapshot,{scopeName}-----{ options2.Value}");
    var options3 = scope.ServiceProvider.GetService<IOptionsSnapshot<UserOptions>>();
    Console.WriteLine($"配置文件根據(jù)名稱讀取,IOptionsSnapshot,{scopeName}-----{ options3.Get("config")}");

    var options4 = scope.ServiceProvider.GetService<IOptionsMonitor<UserOptions>>();
    Console.WriteLine($"配置文件讀取,IOptionsMonitor,{scopeName}-----{ options4.CurrentValue}");
    var options5 = scope.ServiceProvider.GetService<IOptionsMonitor<UserOptions>>();
    Console.WriteLine($"配置文件根據(jù)名稱讀取,IOptionsMonitor,{scopeName}-----{options5.Get("config")}");

    var options6 = scope.ServiceProvider.GetService<IOptions<UserOptions2>>();
    Console.WriteLine($"Options2-----{options6.Value}");
}

public static IServiceCollection Configure<TOptions>(this IServiceCollection services, Action<TOptions> configureOptions) where TOptions : class
{
    return services.Configure(Microsoft.Extensions.Options.Options.DefaultName, configureOptions);
}

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

public static IServiceCollection AddOptions(this IServiceCollection 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;
}

public ConfigureNamedOptions(string name, Action<TOptions> action)
{
 Name = name;
 Action = action;
}

private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(StringComparer.Ordinal);

public TOptions Value => Get(Options.DefaultName);

public virtual TOptions Get(string name)
{
 name = name ?? Options.DefaultName;
 return _cache.GetOrAdd(name, () => _factory.Create(name));
}

public OptionsFactory(IEnumerable<IConfigureOptions<TOptions>> setups, IEnumerable<IPostConfigureOptions<TOptions>> postConfigures)
 {
        _setups = setups;
        _postConfigures = postConfigures;
 }

 public TOptions Create(string name)
 {
        //首先創(chuàng)建對應Options的實例
  TOptions val = Activator.CreateInstance<TOptions>();
        //循環(huán)所有的配置項，依次執(zhí)行，如果對同一個Options配置了多次，最后一次的賦值生效
  foreach (IConfigureOptions<TOptions> setup in _setups)
  {
   var configureNamedOptions = setup as IConfigureNamedOptions<TOptions>;
   if (configureNamedOptions != null)
   {
                //Configure中會判斷傳入Name的值與本身的Name值是否相同，不同則不執(zhí)行Action
                //這解釋了我們一開始的示例中，注入了三個UserOptions，但是在IOptionsSnapshot.Value中獲取到的是第一個沒有名字的
                //因為Value會調(diào)用OptionsManager.Get(Options.DefaultName),進而調(diào)用Factory的Create(Options.DefaultName)
    configureNamedOptions.Configure(name, val);
   }
   else if (name == Options.DefaultName)
   {
    setup.Configure(val);
   }
  }
        
        //PostConfigure沒啥可多說了,名字判斷邏輯與Configure一樣
  foreach (var postConfigure in _postConfigures)
  {
   postConfigure.PostConfigure(name, val);
  }
  
  return val;
 }

public static IServiceCollection Configure<TOptions>(this IServiceCollection services, string name, IConfiguration config, Action<BinderOptions> configureBinder) where TOptions : class
{
 services.AddOptions();
 services.AddSingleton((IOptionsChangeTokenSource<TOptions>)new ConfigurationChangeTokenSource<TOptions>(name, config));
 return services.AddSingleton((IConfigureOptions<TOptions>)new NamedConfigureFromConfigurationOptions<TOptions>(name, config, configureBinder));
}

 public NamedConfigureFromConfigurationOptions(string name, IConfiguration config, Action<BinderOptions> configureBinder)
  : base(name, (Action<TOptions>)delegate(TOptions options)
  {
   config.Bind(options, configureBinder);
  })

//構(gòu)造函數(shù)
public OptionsMonitor(IOptionsFactory<TOptions> factory, IEnumerable<IOptionsChangeTokenSource<TOptions>> sources, IOptionsMonitorCache<TOptions> cache)
{
    _factory = factory;
    _sources = sources;
    _cache = cache;
    //循環(huán)屬于TOptions的所有IChangeToken
    foreach (IOptionsChangeTokenSource<TOptions> source in _sources)
    {
        ChangeToken.OnChange(() => source.GetChangeToken(), delegate(string name)
                             {

                                //清除緩存 
                                name = name ?? Options.DefaultName;
        _cache.TryRemove(name);
                             }, source.Name);
    }
}

 

public virtual TOptions Get(string name)
{
    name = name ?? Options.DefaultName;
    return _cache.GetOrAdd(name, () => _factory.Create(name));
}