如何将侦听器附加到在密钥过期时调用的 MemoryCache？

Question

我在我的一个项目中使用 MemoryCache 来缓存一些键和值。

private bool CacheEntries<T>(MemoryCache memoryCache, string cacheKey, T value, Configuration config, Action<MemoryCacheEntryOptions> otherOptions = null)
{
    int minutes = randomGenerator.Next(config.LowTime, config.HighTime);

    MemoryCacheEntryOptions options = new MemoryCacheEntryOptions()
    {
        Size = config.Size,
        Priority = config.Priority,
        AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(minutes)
    };

    if (otherOptions != null) otherOptions(options);

    CacheKeys.Add(cacheKey);
    memoryCache.Set<T>(cacheKey, value, options);

    return true;
}

如上所示，我的密钥已过期。此外，我将相同的密钥存储在 CacheKeys HashSet 数据结构中供以后使用。有什么方法可以在我的 MemoryCache 上附加一个侦听器，只要它使任何项目过期，就应该调用该侦听器，以便我也可以从 CacheKeys HashSet 中删除这些键。基本上我想与 CacheKeys 和 MemoryCache.

中的内容保持一致

这可以吗？

Answer 1

您似乎在使用来自 Microsoft.Extensions.Caching.Memory 的平台扩展对象。当您在缓存中设置项目的值时，您可以对 MemoryCacheEntryOptions 对象使用 MemoryCacheEntryOptions.PostEvictionCallbacks 属性：

Gets or sets the callbacks will be fired after the cache entry is evicted from the cache.

或者，如果您可以更改为 MemoryCache 的 System.Runtime.Caching 版本，则可以在设置值时使用 CacheItemPolicy。来自 the documentation:

A CacheItemPolicy instance contains information that can be associated with a cache entry. For example, when a cache entry is about to be removed from the cache, a CacheEntryUpdateArguments object is passed to a callback method. The UpdatedCacheItemPolicy property of the CacheEntryUpdateArguments object can pass a reference to a CacheItemPolicy instance that can include eviction and expiration details about the cache entry.

该版本 MemoryCache 的另一种选择是调用 CreateCacheEntryChangeMonitor:

The CreateCacheEntryChangeMonitor method creates a CacheEntryChangeMonitor instance. This specialized change monitor is used to monitor the cache entries that are specified in the keys collection and to trigger events when the entries change.

A monitored entry is considered to have changed for any of the following reasons:

The key does not exist at the time of the call to the CreateCacheEntryChangeMonitor method. In that case, the resulting CacheEntryChangeMonitor instance is immediately set to a changed state. This means that when code subsequently binds a change-notification callback, the callback is triggered immediately.

The associated cache entry was removed from the cache. This can occur if the entry is explicitly removed, if it expires, or if it is evicted to recover memory

如何将侦听器附加到在密钥过期时调用的 MemoryCache？

How to attach a listener to MemoryCache which gets called on expiration of keys?

c#

memorycache