blocks|key|3948117|text|缓存类和接口没有任何方法来清除它们来迭代键，因为它不意味着是一个列表，并且在ASP.NET核心应用程序中通常使用IDistributedCache接口作为依赖项，因为它更容易让您稍后从本地内存缓存更改为分布式缓存(如memd或Redis)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3948118|相反，如果要使特定行无效，则应通过cache.Remove(myKey)删除缓存的条目。|3948119|当然，这需要您知道要使其无效的密钥。通常，您可以通过事件来实现这一点。每次更新数据库中的条目时，都会触发一个事件。此事件将被后台服务捕获并导致缓存无效。|3948120|在本地，这可以通过任何pub/sub库来完成。在分布式场景中，您可能希望使用分布式缓存(即Redis)的发布/订阅功能。|3948121|在查找表的情况下(其中很多值都会受到影响)，您可以让服务刷新缓存(即每隔5到10分钟通过使用诸如hangfire或quart.net的调度库的后台任务)。|3948122|家庭作业问题|3948123|但是您应该问自己一个问题:如果文档频繁更改，那么将文档缓存24小时真的是一个好主意吗？|3948124|加载单个文档是否花费了如此多的时间，以至于24小时缓存它是值得的？或者更短的时间(15分钟、30分钟、60分钟)就足够了？|3948125|entityMap^0|1K|H|0|H|J|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|11|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|12|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|13|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|14|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|15|8|@]|D|@]|E|$]]|$1|R|3|S|5|6|7|16|8|@]|D|@]|E|$]]|$1|T|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|U|$]]

The cache class and interface don't have any methods for clearing neither ones to iterate over the keys, since it's not meant to be a list and in ASP.NET Core applications one usually use <code>IDistributedCache</code> interface as dependency, since it easier allows you to later change from a local memory cache to a distributed cache (such as memd or Redis).
Instead, if you want to invalidate a specific row, you should remove the cached entry via <code>cache.Remove(myKey)</code>.
Of course, this requires you to know the key you want to invalidate. Typically you do that via events. Every time you update an entry in the database, you would fire up an event. This event will be caught by a background service and cause a cache invalidation.
Locally this can be done with any pub/sub library. In distributed scenarios you may want to use pub/sub features of the distributed cache (i.e. Redis).
In cases of lookup tables (where many values are affected), you can have a service refresh the cache (i.e. every 5 to 10 minutes via a background task using a scheduling library such as hangfire or quart.net).
<h2>Home work Questions</h2>
But one question you should ask yourself: Is it really a good idea to cache documents for 24 hours if they change frequently?
Does the loading of a single document takes so much time, that caching it 24 hours will be worth? Or are shorter times good enough (15, 30, 60 minutes)?

blocks|key|3948163|text|要清除你的MemoryCache，只需按键移除内存缓存，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3948164|memoryCache.Remove("your_key");|offset|length|style|CODE|3948165|entityMap^0|0|0|V|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

To clear you MemoryCache, just remove your memory cache by key, like this: 

<code>memoryCache.Remove("your_key");</code>

blocks|key|3948232|text|IMemoryCache确实缺少Clear()方法，但是自己实现一个并不难。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3948233|++++public+class+CacheWrapper
++++{
++++++++private+readonly+IMemoryCache+_memoryCache;
++++++++private+CancellationTokenSource+_resetCacheToken+=+new();

++++++++public+CacheWrapper(IMemoryCache+memoryCache)
++++++++{
++++++++++++_memoryCache+=+memoryCache;
++++++++}

++++++++public+void+Add(object+key,+object+value,+MemoryCacheEntryOptions+memoryCacheEntryOptions)
++++++++{
++++++++++++using+var+entry+=+_memoryCache.CreateEntry(key);
++++++++++++entry.SetOptions(memoryCacheEntryOptions);
++++++++++++entry.Value+=+value;

++++++++++++//+add+an+expiration+token+that+allows+us+to+clear+the+entire+cache+with+a+single+method+call
++++++++++++entry.AddExpirationToken(new+CancellationChangeToken(_resetCacheToken.Token));
++++++++}

++++++++public+void+Clear()
++++++++{
++++++++++++_resetCacheToken.Cancel();+//+this+triggers+the+CancellationChangeToken+to+expire+every+item+from+cache

++++++++++++_resetCacheToken.Dispose();+//+dispose+the+current+cancellation+token+source+and+create+a+new+one
++++++++++++_resetCacheToken+=+new+CancellationTokenSource();
++++++++}
++++}|code-block|syntax|javascript|3948234|基于https://docs.microsoft.com/en-us/aspnet/core/performance/caching/memory?view=aspnetcore-3.1#cache-dependencies和https://stackoverflow.com/a/45543023/2078975|3948235|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.microsoft.com/en-us/aspnet/core/performance/caching/memory?view=aspnetcore-3.1#cache-dependencies|1|https://stackoverflow.com/a/45543023/2078975^0|0|C|G|7|0|0|2|32|0|35|18|1|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@]|D|@$9|13|A|14|1|15]|$9|16|A|17|1|18]]|E|$]]|$1|M|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]|U|$5|P|Q|R|E|$S|V]]]]

<code>IMemoryCache</code> indeed lacks a <code>Clear()</code> method, but it's not hard to implement one yourself.
<pre><code> public class CacheWrapper
 {
 private readonly IMemoryCache _memoryCache;
 private CancellationTokenSource _resetCacheToken = new();

 public CacheWrapper(IMemoryCache memoryCache)
 {
 _memoryCache = memoryCache;
 }

 public void Add(object key, object value, MemoryCacheEntryOptions memoryCacheEntryOptions)
 {
 using var entry = _memoryCache.CreateEntry(key);
 entry.SetOptions(memoryCacheEntryOptions);
 entry.Value = value;

 // add an expiration token that allows us to clear the entire cache with a single method call
 entry.AddExpirationToken(new CancellationChangeToken(_resetCacheToken.Token));
 }

 public void Clear()
 {
 _resetCacheToken.Cancel(); // this triggers the CancellationChangeToken to expire every item from cache

 _resetCacheToken.Dispose(); // dispose the current cancellation token source and create a new one
 _resetCacheToken = new CancellationTokenSource();
 }
 }

</code></pre>
Based on <a href="https://docs.microsoft.com/en-us/aspnet/core/performance/caching/memory?view=aspnetcore-3.1#cache-dependencies" rel="nofollow noreferrer">https://docs.microsoft.com/en-us/aspnet/core/performance/caching/memory?view=aspnetcore-3.1#cache-dependencies</a> and <a href="https://stackoverflow.com/a/45543023/2078975">https://stackoverflow.com/a/45543023/2078975</a>

How to correctly clear IMemoryCache from ASP.NET Core?

I believe this class is missing Clear method, but anyway how to deal with it? In my project I'm caching DocumentRepository's methods for 24 hours where I'm getting lots of rows from database. But sometimes I can change the database, so I want to clear the IMemoryCache as it has got rubbish data.

How to clear MemoryCache in ASP.NET Core?

数据库

Redis

如何正确清除ASP.NET内核中的IMemoryCache？我相信这个类缺少清晰的方法，但无论如何如何处理它呢？在我的项目中，我对DocumentRepository的方法进行了24小时的缓存，从数据库中获得了很多行。但有时我可以更改数据库，所以我想清除IMemoryCache，因为它有垃圾数据。

问如何清除ASP.NET内核中的MemoryCache？
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