Application_End() 无法通过 HttpContext.Current.Cache[key] 访问缓存

发布于 2024-10-07 15:21:27 字数 496 浏览 10 评论 0原文

我希望能够在应用程序重新启动之间维护某些对象。

为此，我想在 Global.asax Application_End() 函数中将特定的缓存项写入磁盘，并在 Application_Start() 上重新加载它们。

我目前有一个缓存助手类，它使用以下方法返回缓存的值：

return HttpContext.Current.Cache[key];

问题：在Application_End()期间，HttpContext.Current为 null，因为没有 Web 请求（这是一个自动清理过程） - 因此，我无法访问 .Cache[] 来检索任何要保存到磁盘的项目。

问题：如何在 Application_End() 期间访问缓存项？

原文

I want to be able to maintain certain objects between application restarts.

To do that, I want to write specific cached items out to disk in Global.asax Application_End() function and re-load them back on Application_Start().

I currently have a cache helper class, which uses the following method to return the cached value:

return HttpContext.Current.Cache[key];

Problem: during Application_End(), HttpContext.Current is null since there is no web request (it's an automated cleanup procedure) - therefore, I cannot access .Cache[] to retrieve any of the items to save to disk.

Question: how can I access the cache items during Application_End()?

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睫毛溺水了 2024-10-14 15:21:28

作为替代解决方案，您可以将数据存储在应用程序对象（应用程序[key]）中，或者简单地创建一个静态类并使用它来将数据保存在应用程序中 - 在这种情况下，数据仍然可用在Application_End 时。

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风吹过旳痕迹 2024-10-14 15:21:27

如果您想在缓存对象被释放之前访问它，您需要使用类似这样的方式将对象添加到缓存：

将命名空间 System.Web.Caching 导入到您正在使用添加对象到缓存的应用程序。

//Add callback method to delegate
var onRemove = new CacheItemRemovedCallback(RemovedCallback);

//Insert object to cache
HttpContext.Current.Cache.Insert("YourKey", YourValue, null, DateTime.Now.AddHours(12), Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, onRemove);

当要释放该对象时，将调用以下方法：

private void RemovedCallback(string key, object value, CacheItemRemovedReason reason)
{
    //Use your logic here

    //After this method cache object will be disposed
}

If you want to get access to cache object before it will be disposed, you need to use somethink like this to add object to cache:

Import namespace System.Web.Caching to your application where you are using adding objects to cache.

//Add callback method to delegate
var onRemove = new CacheItemRemovedCallback(RemovedCallback);

//Insert object to cache
HttpContext.Current.Cache.Insert("YourKey", YourValue, null, DateTime.Now.AddHours(12), Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, onRemove);

And when this object is going to be disposed will be called following method:

private void RemovedCallback(string key, object value, CacheItemRemovedReason reason)
{
    //Use your logic here

    //After this method cache object will be disposed
}

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风和你 2024-10-14 15:21:27

我强烈敦促您重新考虑您的方法。您可能想描述您想要做什么的具体细节，以便我们可以帮助您。
但是，如果您完全确定了它，那么您可以在实际设置值时将它们保存在磁盘上，即您的帮助器类将如下所示：

public static class CacheHelper
{
    public static void SetCache(string key, object value)
    {
        HttpContext.Current.Cache[key] = value;
        if (key == "some special key")
            WriteValueOnDisk(value);
    }
}

I strongly urge you to rethink your approach. You may want to describe specifics of what are you trying to do, so we might help you with that.
But if you are totally set on it, then you can simply save values on disk when you actually set them, i.e. your helper class would looks something like this:

public static class CacheHelper
{
    public static void SetCache(string key, object value)
    {
        HttpContext.Current.Cache[key] = value;
        if (key == "some special key")
            WriteValueOnDisk(value);
    }
}

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