Asp.net core中實現自動更新的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;
 // 這里采用硬編碼指定option的路徑
 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實例, 有參數發生了改變
 isChanged = false;
 }
 }
 //判斷兩個Idictionary是否有不同的幫助方法
 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() };
 }
}