Asp.net core中实现自动更新的Option的方法示例

public class RefreshableOptions
{
  public int IncreasementCount { get; set; }
}

public class AutoRefreshConfigurationSource : IConfigurationSource
{
  public IConfigurationProvider Build(IConfigurationBuilder builder)
  {
    return new AutoRefreshConfigurationProvider();
  }
}

public class AutoRefreshConfigurationProvider : ConfigurationProvider
{
  private int count = 0;
  private bool isChanged;

  public AutoRefreshConfigurationProvider() : base()
  {
    Timer timer = new Timer(TimerCallback);
    timer.Change(1000, 3000);
  }

  public override void Load()
  {
    var beforeData = Data;
    // 这里采用硬编码指定option的路径
    Data = new Dictionary<string, string>() { { "AutoRefreshOptions:IncreasementCount", count.ToString() } };
    isChanged = IsDictionaryChanged(beforeData, Data);
  }

  private void TimerCallback(object state)
  {
    count++;
    this.Load();
    if (isChanged)
    {
      base.OnReload();//通知IConfiguration实例, 有参数发生了改变
      isChanged = false;
    }
  }
  //判断两个Idictionary是否有不同的帮助方法
  private static bool IsDictionaryChanged(IDictionary<string, string> before, IDictionary<string, string> after)
  {
    if (before == null && after == null)
    {
      return false;
    }
    if ((before == null) != (after == null))
    {
      return true;
    }
    if (before.Count != after.Count)
    {
      return true;
    }
    var ignoreCaseBefore = new Dictionary<string, string>(before, StringComparer.OrdinalIgnoreCase);
    foreach (var afterItemKey in after.Keys)
    {
      if (!ignoreCaseBefore.TryGetValue(afterItemKey, out var beforeItemValue))
      {
        return true;
      }
      if (beforeItemValue != after[afterItemKey])
      {
        return true;
      }
      ignoreCaseBefore.Remove(afterItemKey);
    }
    if (ignoreCaseBefore.Count > 0)
    {
      return true;
    }
    return false;
  }
}

public static class AutoRereshConfigurationExtensions
{
  public static IConfigurationBuilder AddAutoRereshConfiguration(this IConfigurationBuilder builder)
  {
    return builder.Add(new AutoRefreshConfigurationSource());
  }
}

WebHost.CreateDefaultBuilder(args)
  .ConfigureAppConfiguration(config =>
  {
    config.AddAutoRereshConfiguration();
  })
  .UseStartup<Startup>();

services.Configure<RefreshableOptions>(Configuration.GetSection("AutoRefreshOptions"));

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
  private RefreshableOptions refreshableOptions;
  public ValuesController(IOptionsSnapshot<RefreshableOptions> refreshableOptions)
  {
    this.refreshableOptions = refreshableOptions.Value;
  }

  [HttpGet]
  public ActionResult<IEnumerable<string>> Get()
  {
    return new string[] { "value1", "value2", refreshableOptions.IncreasementCount.ToString() };
  }
}