Asp.net core 手动触发IOptionsMonitor<>；。一旦改变

在ASP.NET Core 2.1中，我使用IOptionsMonitor并对其进行设置，以便在更改appSettings.json文件时成功获取事件。所以这是有效的

我现在想做的是，通过代码手动更改选项中的一些值，并触发所有监视器。这可能吗？

对于

IOptionsMonitor

，它只会更改内存中的值，而不会保存回

appsettings.json

。为了解决这个问题，您需要实现自己的方法将更改保存回

appsettings.json

• 定义从

  IOptions继承的
  IWritableOptions
  
  public interface IWritableOptions<out T> : IOptions<T> where T : class, new()
  {
       void Update(Action<T> applyChanges);
  }
  
  public class WritableOptions<T> : IWritableOptions<T> where T : class, new()
  {
  private readonly IHostingEnvironment _environment;
  private readonly IOptionsMonitor<T> _options;
  private readonly IConfigurationRoot _configuration;
  private readonly string _section;
  private readonly string _file;
  
  public WritableOptions(
      IHostingEnvironment environment,
      IOptionsMonitor<T> options,
      IConfigurationRoot configuration,
      string section,
      string file)
  {
      _environment = environment;
      _options = options;
      _configuration = configuration;
      _section = section;
      _file = file;
  }
  
  public T Value => _options.CurrentValue;
  public T Get(string name) => _options.Get(name);
  
  public void Update(Action<T> applyChanges)
  {
      var fileProvider = _environment.ContentRootFileProvider;
      var fileInfo = fileProvider.GetFileInfo(_file);
      var physicalPath = fileInfo.PhysicalPath;
  
      var jObject = JsonConvert.DeserializeObject<JObject>(File.ReadAllText(physicalPath));
      var sectionObject = jObject.TryGetValue(_section, out JToken section) ?
          JsonConvert.DeserializeObject<T>(section.ToString()) : (Value ?? new T());
  
      applyChanges(sectionObject);
  
      jObject[_section] = JObject.Parse(JsonConvert.SerializeObject(sectionObject));
      File.WriteAllText(physicalPath, JsonConvert.SerializeObject(jObject, Formatting.Indented));
      _configuration.Reload();
  }
  }
  
  

• 配置

  IWritableOptions

  public static class ServiceCollectionExtensions
  {
  public static void ConfigureWritable<T>(
      this IServiceCollection services,
      IConfigurationSection section,
      string file = "appsettings.json") where T : class, new()
  {
      services.Configure<T>(section);
      services.AddTransient<IWritableOptions<T>>(provider =>
      {
          var configuration = (IConfigurationRoot)provider.GetService<IConfiguration>();
          var environment = provider.GetService<IHostingEnvironment>();
          var options = provider.GetService<IOptionsMonitor<T>>();
          return new WritableOptions<T>(environment, options, configuration, section.Key, file);
      });
  }
  }
  

• 使用

  public class OptionsController : Controller
  {
  private readonly IWritableOptions<Locations> _writableLocations;
  public OptionsController(IWritableOptions<Locations> writableLocations)
  {
      _writableLocations = writableLocations;
  }
  
  public IActionResult Change(string value)
  {
      _writableLocations.Update(opt => {
          opt.Name = value;
      });
      return Ok("OK");
  }
  }
  

  公共类选项控制器：控制器
  {
  私有只读IWritableOptions\u writableLocations；
  公共选项控制器（IWritableOptions可写位置）
  {
  _writableLocations=可写位置；
  }
  公共IActionResult更改（字符串值）
  {
  _writableLocations.Update（opt=>{
  opt.Name=值；
  });
  返回Ok（“Ok”）；
  }
  }
  

• 它将触发

  IOptionsMonitor.OnChange

对于

IOptionsMonitor

，它只更改内存中的值，而不保存回

appsettings.json

。为了解决这个问题，您需要实现自己的方法将更改保存回

appsettings.json

• 定义从

  IOptions继承的
  IWritableOptions
  
  public interface IWritableOptions<out T> : IOptions<T> where T : class, new()
  {
       void Update(Action<T> applyChanges);
  }
  
  public class WritableOptions<T> : IWritableOptions<T> where T : class, new()
  {
  private readonly IHostingEnvironment _environment;
  private readonly IOptionsMonitor<T> _options;
  private readonly IConfigurationRoot _configuration;
  private readonly string _section;
  private readonly string _file;
  
  public WritableOptions(
      IHostingEnvironment environment,
      IOptionsMonitor<T> options,
      IConfigurationRoot configuration,
      string section,
      string file)
  {
      _environment = environment;
      _options = options;
      _configuration = configuration;
      _section = section;
      _file = file;
  }
  
  public T Value => _options.CurrentValue;
  public T Get(string name) => _options.Get(name);
  
  public void Update(Action<T> applyChanges)
  {
      var fileProvider = _environment.ContentRootFileProvider;
      var fileInfo = fileProvider.GetFileInfo(_file);
      var physicalPath = fileInfo.PhysicalPath;
  
      var jObject = JsonConvert.DeserializeObject<JObject>(File.ReadAllText(physicalPath));
      var sectionObject = jObject.TryGetValue(_section, out JToken section) ?
          JsonConvert.DeserializeObject<T>(section.ToString()) : (Value ?? new T());
  
      applyChanges(sectionObject);
  
      jObject[_section] = JObject.Parse(JsonConvert.SerializeObject(sectionObject));
      File.WriteAllText(physicalPath, JsonConvert.SerializeObject(jObject, Formatting.Indented));
      _configuration.Reload();
  }
  }
  
  

• 配置

  IWritableOptions

  public static class ServiceCollectionExtensions
  {
  public static void ConfigureWritable<T>(
      this IServiceCollection services,
      IConfigurationSection section,
      string file = "appsettings.json") where T : class, new()
  {
      services.Configure<T>(section);
      services.AddTransient<IWritableOptions<T>>(provider =>
      {
          var configuration = (IConfigurationRoot)provider.GetService<IConfiguration>();
          var environment = provider.GetService<IHostingEnvironment>();
          var options = provider.GetService<IOptionsMonitor<T>>();
          return new WritableOptions<T>(environment, options, configuration, section.Key, file);
      });
  }
  }
  

• 使用

  public class OptionsController : Controller
  {
  private readonly IWritableOptions<Locations> _writableLocations;
  public OptionsController(IWritableOptions<Locations> writableLocations)
  {
      _writableLocations = writableLocations;
  }
  
  public IActionResult Change(string value)
  {
      _writableLocations.Update(opt => {
          opt.Name = value;
      });
      return Ok("OK");
  }
  }
  

  公共类选项控制器：控制器
  {
  私有只读IWritableOptions\u writableLocations；
  公共选项控制器（IWritableOptions可写位置）
  {
  _writableLocations=可写位置；
  }
  公共IActionResult更改（字符串值）
  {
  _writableLocations.Update（opt=>{
  opt.Name=值；
  });
  返回Ok（“Ok”）；
  }
  }
  

• 它将触发

  IOptionsMonitor.OnChange

---

当您说“对于IOptionsMonitor，它只更改内存中的值…”时，意味着它将作为缓存值使用？。它可以使用多长时间？@D.B当应用程序重新启动或回收时，它将丢失。当你说“对于IOptionsMonitor，它只更改内存中的值…”时，意味着它将作为缓存值使用？。它将可用多长时间？@D.B当应用程序重新启动或回收时，它将丢失。