Options是微软提供的选项模块，该模块依赖于容器使用。除了微软的IServiceCollection，当然也可以使用其它的依赖注入容器。本文演示如何在prism中使用Options。

创建应用项目

创建一个Avalonia应用（或其它类型应用），然后使用NuGet包管理器添加Prism.DryIoc.Avalonia包。创建Views和ViewModels文件夹，将MainWindow移动到Views文件夹中（注意修改namespace），在ViewModels文件夹中创建MainWindowViewModel，以便Prism自动绑定ViewModel。

public partial class App : PrismApplication
{
    public override void Initialize()
    {
        AvaloniaXamlLoader.Load(this);
        base.Initialize();
    }

    protected override AvaloniaObject CreateShell()
    {
        return Container.Resolve<MainWindow>();
    }

    protected override void RegisterTypes(IContainerRegistry containerRegistry)
    {
        containerRegistry.Register<MainWindow>();
    }
}

添加Options功能

• 首先使用NuGet添加Microsoft.Extentions.Options和Microsoft.Extensions.Options.ConfigurationExtensions。使用json配置文件进行测试，因此再添加上Microsoft.Extensions.Configuration.Json及Microsoft.Extensions.Configuration.Binder。

• 添加Options静态类，提供DefaultName：

  public static class Options { public static readonly string DefaultName = string.Empty; internal const DynamicallyAccessedMemberTypes DynamicallyAccessedMembers = DynamicallyAccessedMemberTypes.PublicParameterlessConstructor; }

• 由于UnnamedOptionsManager为内部类，无法直接使用，因此添加一个UnnamedOptionsManager类，实现IOptions<>接口，直接拷贝源码即可：

  public class UnnamedOptionsManager<[DynamicallyAccessedMembers(Options.DynamicallyAccessedMembers)] TOptions> : IOptions where TOptions : class { private readonly IOptionsFactory _factory; private volatile object _syncObj; private volatile TOptions _value;

  public UnnamedOptionsManager(IOptionsFactory<TOptions> factory) => _factory = factory;
  
  
  public TOptions Value
  {
      get
      {
          if (_value is TOptions value)
              return value;
  
  
          lock (_syncObj ?? Interlocked.CompareExchange(ref _syncObj, new object(), null) ?? _syncObj)
          {
              return _value ??= _factory.Create(Options.DefaultName);
          }
      }
  }
  

  }

• 添加OptionsPrismExtensions扩展类，添加AddOptions扩展方法，将选项泛型接口、工厂、缓存注册到容器中。工厂注册为瞬时，其它注册为单例。客户端不需要添加IOptionsSnapshot，只添加IOptions<>和IOptionsMonitor<>即可，前者获取选项不会监听修改，后者可以监听选项修改：

  public static class OptionsPrismExtensions { public static IContainerExtension AddOptions(this IContainerExtension container) { ArgumentNullException.ThrowIfNull(container, nameof(container));

      container.RegisterSingleton(typeof(IOptions<>), typeof(UnnamedOptionsManager<>));
      container.RegisterSingleton(typeof(IOptionsMonitor<>), typeof(OptionsMonitor<>));
      container.Register(typeof(IOptionsFactory<>), typeof(OptionsFactory<>));
      container.RegisterSingleton(typeof(IOptionsMonitorCache<>), typeof(OptionsCache<>));
      return container;
  }
  

  }

• 添加OptionsConfigurationPrismExtensions扩展类，提供Configuration相关的扩展方法，可以直接将选项和配置Section进行绑定：

  public static class OptionsConfigurationPrismExtensions { public static IContainerExtension Configure<[DynamicallyAccessedMembers( DynamicallyAccessedMemberTypes.All)] TOptions>(this IContainerExtension container, IConfiguration config) where TOptions : class => container.Configure(Options.DefaultName, config, _ => { });

  public static IContainerExtension Configure<[DynamicallyAccessedMembers(
      DynamicallyAccessedMemberTypes.All)] TOptions>(this IContainerExtension container, 
      string name, IConfiguration config, Action<BinderOptions> configureBinder)
      where TOptions : class
  {
      ArgumentNullException.ThrowIfNull(container, nameof(container));
      ArgumentNullException.ThrowIfNull(config, nameof(config));
  
  
      container.AddOptions();
      container.RegisterInstance<IOptionsChangeTokenSource<TOptions>>(
          new ConfigurationChangeTokenSource<TOptions>(name, config));
      container.RegisterInstance<IConfigureOptions<TOptions>>(
          new NamedConfigureFromConfigurationOptions<TOptions>(name, config, configureBinder));
  
  
      return container;
  }
  

  }

使用

• 添加一个settings.json配置文件，设置属性复制到输出目录：如果较新则复制：

  { “Test”: { “Name”: “louzi”, “Age”: 18, “Sex”: “Male” } }

• 添加Test对应的Option实体：

  public class TestOption { public string Name { get; set; }

  public int Age { get; set; }
  
  
  public Gender Sex { get; set; }
  

  }

  public enum Gender { Male, Female }

• 创建IConfiguration并绑定到选项：

  // App protected override IContainerExtension CreateContainerExtension() { var container = base.CreateContainerExtension();

  IConfiguration config = new ConfigurationBuilder().SetBasePath(Directory.GetCurrentDirectory())
      .AddJsonFile("settings.json", optional: true, reloadOnChange: true).Build();
  container.AddOptions().Configure<TestOption>(config.GetSection("Test"));
  
  
  return container;
  

  }

• ViewModel中通过依赖注入获取选项：

  public class MainWindowViewModel : BindableBase { private string _name; private int _age; private Gender _sex;

  public MainWindowViewModel(IOptions<TestOption> options)
  {
      var testOption = options.Value;
      _name = testOption.Name;
      _age = testOption.Age;
      _sex = testOption.Sex;
  }
  
  
  public string Name { get => _name; set => SetProperty(ref _name, value); }
  
  
  public int Age { get => _age; set => SetProperty(ref _age, value); }
  
  
  public Gender Sex { get => _sex; set => SetProperty(ref _sex, value); }
  

  }

• View中显示

项目结构及运行效果如下图：