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title author description monikerRange ms.author ms.custom ms.date content_well_notification uid ai-usage
Cache in-memory in ASP.NET Core
tdykstra
Learn how to cache data in memory in ASP.NET Core.
>= aspnetcore-3.1
tdykstra
mvc
11/07/2023
AI-contribution
performance/caching/memory
ai-assisted

Cache in-memory in ASP.NET Core

By Rick Anderson, John Luo, and Steve Smith

:::moniker range=">= aspnetcore-6.0"

Caching can significantly improve the performance and scalability of an app by reducing the work required to generate content. Caching works best with data that changes infrequently and is expensive to generate. Caching makes a copy of data that can be returned much faster than from the source. Apps should be written and tested to never depend on cached data.

ASP.NET Core supports several different caches. The simplest cache is based on the xref:Microsoft.Extensions.Caching.Memory.IMemoryCache. IMemoryCache represents a cache stored in the memory of the web server. Apps running on a server farm (multiple servers) should ensure sessions are sticky when using the in-memory cache. Sticky sessions ensure that requests from a client all go to the same server. For example, Azure Web apps use Application Request Routing (ARR) to route all requests to the same server.

Non-sticky sessions in a web farm require a distributed cache to avoid cache consistency problems. For some apps, a distributed cache can support higher scale-out than an in-memory cache. Using a distributed cache offloads the cache memory to an external process.

The in-memory cache can store any object. The distributed cache interface is limited to byte[]. The in-memory and distributed cache store cache items as key-value pairs.

System.Runtime.Caching/MemoryCache

xref:System.Runtime.Caching/xref:System.Runtime.Caching.MemoryCache (NuGet package) can be used with:

  • .NET Standard 2.0 or later.
  • Any .NET implementation that targets .NET Standard 2.0 or later. For example, ASP.NET Core 3.1 or later.
  • .NET Framework 4.5 or later.

Microsoft.Extensions.Caching.Memory/IMemoryCache (described in this article) is recommended over System.Runtime.Caching/MemoryCache because it's better integrated into ASP.NET Core. For example, IMemoryCache works natively with ASP.NET Core dependency injection.

Use System.Runtime.Caching/MemoryCache as a compatibility bridge when porting code from ASP.NET 4.x to ASP.NET Core.

Cache guidelines

  • Code should always have a fallback option to fetch data and not depend on a cached value being available.
  • The cache uses a scarce resource, memory. Limit cache growth:
    • Do not insert external input into the cache. As an example, using arbitrary user-provided input as a cache key is not recommended since the input might consume an unpredictable amount of memory.
    • Use expirations to limit cache growth.
    • Use SetSize, Size, and SizeLimit to limit cache size. The ASP.NET Core runtime does not limit cache size based on memory pressure. It's up to the developer to limit cache size.

Use IMemoryCache

Warning

Using a shared memory cache from Dependency Injection and calling SetSize, Size, or SizeLimit to limit cache size can cause the app to fail. When a size limit is set on a cache, all entries must specify a size when being added. This can lead to issues since developers may not have full control on what uses the shared cache. When using SetSize, Size, or SizeLimit to limit cache, create a cache singleton for caching. For more information and an example, see Use SetSize, Size, and SizeLimit to limit cache size. A shared cache is one shared by other frameworks or libraries.

In-memory caching is a service that's referenced from an app using Dependency Injection. Request the IMemoryCache instance in the constructor:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Pages/Index.cshtml.cs" id="snippet_ClassConstructor" highlight="5":::

The following code uses xref:Microsoft.Extensions.Caching.Memory.IMemoryCache.TryGetValue%2A to check if a time is in the cache. If a time isn't cached, a new entry is created and added to the cache with xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.Set%2A:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Pages/Index.cshtml.cs" id="snippet_OnGet" highlight="5,9-12":::

In the preceding code, the cache entry is configured with a sliding expiration of three seconds. If the cache entry isn't accessed for more than three seconds, it gets evicted from the cache. Each time the cache entry is accessed, it remains in the cache for a further 3 seconds. The CacheKeys class is part of the download sample.

The current time and the cached time are displayed:

:::code language="cshtml" source="memory/samples/6.x/CachingMemorySample/Pages/Index.cshtml" id="snippet_CacheCurrentDateTime":::

The following code uses the Set extension method to cache data for a relative time without MemoryCacheEntryOptions:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_OnGetCacheRelative":::

In the preceding code, the cache entry is configured with a relative expiration of one day. The cache entry gets evicted from the cache after one day, even if it's accessed within this timeout period.

The following code uses xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreate%2A and xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreateAsync%2A to cache data.

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_OnGetCacheGetOrCreate":::

The following code calls xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.Get%2A to fetch the cached time:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_OnGetCacheGet":::

The following code gets or creates a cached item with absolute expiration:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_OnGetCacheGetOrCreateAbsolute" highlight="5":::

A cached item set with only a sliding expiration is at risk of never expiring. If the cached item is repeatedly accessed within the sliding expiration interval, the item never expires. Combine a sliding expiration with an absolute expiration to guarantee the item expires. The absolute expiration sets an upper bound on how long the item can be cached while still allowing the item to expire earlier if it isn't requested within the sliding expiration interval. If either the sliding expiration interval or the absolute expiration time pass, the item is evicted from the cache.

The following code gets or creates a cached item with both sliding and absolute expiration:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_OnGetCacheGetOrCreateSlidingAbsolute" highlight="5-6":::

The preceding code guarantees the data won't be cached longer than the absolute time.

xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreate%2A, xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreateAsync%2A, and xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.Get%2A are extension methods in the xref:Microsoft.Extensions.Caching.Memory.CacheExtensions class. These methods extend the capability of xref:Microsoft.Extensions.Caching.Memory.IMemoryCache.

MemoryCacheEntryOptions

The following example:

  • Sets the cache priority to xref:Microsoft.Extensions.Caching.Memory.CacheItemPriority.NeverRemove?displayProperty=nameWithType.
  • Sets a xref:Microsoft.Extensions.Caching.Memory.PostEvictionDelegate that gets called after the entry is evicted from the cache. The callback is run on a different thread from the code that removes the item from the cache.

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_MemoryCacheEntryOptions" highlight="4-5":::

Use SetSize, Size, and SizeLimit to limit cache size

A MemoryCache instance may optionally specify and enforce a size limit. The cache size limit doesn't have a defined unit of measure because the cache has no mechanism to measure the size of entries. If the cache size limit is set, all entries must specify size. The ASP.NET Core runtime doesn't limit cache size based on memory pressure. It's up to the developer to limit cache size. The size specified is in units the developer chooses.

For example:

  • If the web app was primarily caching strings, each cache entry size could be the string length.
  • The app could specify the size of all entries as 1, and the size limit is the count of entries.

If xref:Microsoft.Extensions.Caching.Memory.MemoryCacheOptions.SizeLimit isn't set, the cache grows without bound. The ASP.NET Core runtime doesn't trim the cache when system memory is low. Apps must be architected to:

  • Limit cache growth.
  • Call xref:Microsoft.Extensions.Caching.Memory.MemoryCache.Compact%2A or xref:Microsoft.Extensions.Caching.Memory.MemoryCache.Remove%2A when available memory is limited.

The following code creates a unitless fixed size xref:Microsoft.Extensions.Caching.Memory.MemoryCache accessible by dependency injection:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/MyMemoryCache.cs" id="snippet_Class":::

SizeLimit doesn't have units. Cached entries must specify size in whatever units they consider most appropriate if the cache size limit has been set. All users of a cache instance should use the same unit system. An entry won't be cached if the sum of the cached entry sizes exceeds the value specified by SizeLimit. If no cache size limit is set, the cache size set on the entry is ignored.

The following code registers MyMemoryCache with the dependency injection container:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Program.cs" id="snippet_AddSingletonMyMemoryCache" highlight="4":::

MyMemoryCache is created as an independent memory cache for components that are aware of this size limited cache and know how to set cache entry size appropriately.

The size of the cache entry can be set using the xref:Microsoft.Extensions.Caching.Memory.MemoryCacheEntryExtensions.SetSize%2A extension method or the xref:Microsoft.Extensions.Caching.Memory.MemoryCacheEntryOptions.Size property:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/MyMemoryCache.cshtml.cs" id="snippet_OnGetCacheSizeSetSize" highlight="4,6":::

In the preceding code, the two highlighted lines achieve the same result of setting the size of the cache entry. SetSize is provided for convenience when chaining calls onto new MemoryCacheOptions().

MemoryCache.Compact

MemoryCache.Compact attempts to remove the specified percentage of the cache in the following order:

  • All expired items.
  • Items by priority. Lowest priority items are removed first.
  • Least recently used objects.
  • Items with the earliest absolute expiration.
  • Items with the earliest sliding expiration.

Pinned items with priority xref:Microsoft.Extensions.Caching.Memory.CacheItemPriority.NeverRemove are never removed. The following code removes a cache item and calls Compact to remove 25% of cached entries:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/MyMemoryCache.cshtml.cs" id="snippet_OnGetCacheCompact":::

For more information, see the Compact source on GitHub.

Cache dependencies

The following sample shows how to expire a cache entry if a dependent entry expires. A xref:Microsoft.Extensions.Primitives.CancellationChangeToken is added to the cached item. When Cancel is called on the CancellationTokenSource, both cache entries are evicted:

:::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_CacheDependencies" highlight="16,24":::

Using a xref:System.Threading.CancellationTokenSource allows multiple cache entries to be evicted as a group. With the using pattern in the code above, cache entries created inside the using scope inherit triggers and expiration settings.

Additional notes

  • Expiration doesn't happen in the background. There's no timer that actively scans the cache for expired items. Any activity on the cache (Get, Set, Remove) can trigger a background scan for expired items. A timer on the CancellationTokenSource (xref:System.Threading.CancellationTokenSource.CancelAfter%2A) also removes the entry and triggers a scan for expired items. The following example uses xref:System.Threading.CancellationTokenSource.%23ctor(System.TimeSpan) for the registered token. When this token fires, it removes the entry immediately and fires the eviction callbacks:

    :::code language="csharp" source="memory/samples/6.x/CachingMemorySample/Snippets/Pages/Index.cshtml.cs" id="snippet_OnGeCacheExpirationToken":::

  • When using a callback to repopulate a cache item:

    • Multiple requests can find the cached key value empty because the callback hasn't completed.
    • This can result in several threads repopulating the cached item.

  • When one cache entry is used to create another, the child copies the parent entry's expiration tokens and time-based expiration settings. The child isn't expired by manual removal or updating of the parent entry.

  • Use xref:Microsoft.Extensions.Caching.Memory.ICacheEntry.PostEvictionCallbacks to set the callbacks that will be fired after the cache entry is evicted from the cache.

  • For most apps, IMemoryCache is enabled. For example, calling AddMvc, AddControllersWithViews, AddRazorPages, AddMvcCore().AddRazorViewEngine, and many other Add{Service} methods in Program.cs, enables IMemoryCache. For apps that don't call one of the preceding Add{Service} methods, it may be necessary to call xref:Microsoft.Extensions.DependencyInjection.MemoryCacheServiceCollectionExtensions.AddMemoryCache%2A in Program.cs.

Background cache update

Use a background service such as xref:Microsoft.Extensions.Hosting.IHostedService to update the cache. The background service can recompute the entries and then assign them to the cache only when they’re ready.

Additional resources

  • View or download sample code (how to download)
  • xref:performance/caching/distributed
  • xref:fundamentals/change-tokens
  • xref:performance/caching/response
  • xref:performance/caching/middleware
  • xref:mvc/views/tag-helpers/builtin-th/cache-tag-helper
  • xref:mvc/views/tag-helpers/builtin-th/distributed-cache-tag-helper

:::moniker-end

:::moniker range="< aspnetcore-6.0"

View or download sample code (how to download)

Caching basics

Caching can significantly improve the performance and scalability of an app by reducing the work required to generate content. Caching works best with data that changes infrequently and is expensive to generate. Caching makes a copy of data that can be returned much faster than from the source. Apps should be written and tested to never depend on cached data.

ASP.NET Core supports several different caches. The simplest cache is based on the xref:Microsoft.Extensions.Caching.Memory.IMemoryCache. IMemoryCache represents a cache stored in the memory of the web server. Apps running on a server farm (multiple servers) should ensure sessions are sticky when using the in-memory cache. Sticky sessions ensure that subsequent requests from a client all go to the same server. For example, Azure Web apps use Application Request Routing (ARR) to route all subsequent requests to the same server.

Non-sticky sessions in a web farm require a distributed cache to avoid cache consistency problems. For some apps, a distributed cache can support higher scale-out than an in-memory cache. Using a distributed cache offloads the cache memory to an external process.

The in-memory cache can store any object. The distributed cache interface is limited to byte[]. The in-memory and distributed cache store cache items as key-value pairs.

System.Runtime.Caching/MemoryCache

xref:System.Runtime.Caching/xref:System.Runtime.Caching.MemoryCache (NuGet package) can be used with:

  • .NET Standard 2.0 or later.
  • Any .NET implementation that targets .NET Standard 2.0 or later. For example, ASP.NET Core 3.1 or later.
  • .NET Framework 4.5 or later.

Microsoft.Extensions.Caching.Memory/IMemoryCache (described in this article) is recommended over System.Runtime.Caching/MemoryCache because it's better integrated into ASP.NET Core. For example, IMemoryCache works natively with ASP.NET Core dependency injection.

Use System.Runtime.Caching/MemoryCache as a compatibility bridge when porting code from ASP.NET 4.x to ASP.NET Core.

Cache guidelines

  • Code should always have a fallback option to fetch data and not depend on a cached value being available.
  • The cache uses a scarce resource, memory. Limit cache growth:

Use IMemoryCache

Warning

Using a shared memory cache from Dependency Injection and calling SetSize, Size, or SizeLimit to limit cache size can cause the app to fail. When a size limit is set on a cache, all entries must specify a size when being added. This can lead to issues since developers may not have full control on what uses the shared cache. When using SetSize, Size, or SizeLimit to limit cache, create a cache singleton for caching. For more information and an example, see Use SetSize, Size, and SizeLimit to limit cache size. A shared cache is one shared by other frameworks or libraries.

In-memory caching is a service that's referenced from an app using Dependency Injection. Request the IMemoryCache instance in the constructor:

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet_ctor":::

The following code uses xref:Microsoft.Extensions.Caching.Memory.IMemoryCache.TryGetValue%2A to check if a time is in the cache. If a time isn't cached, a new entry is created and added to the cache with xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.Set%2A. The CacheKeys class is part of the download sample.

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/CacheKeys.cs":::

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet1":::

The current time and the cached time are displayed:

:::code language="cshtml" source="memory/samples/3.x/WebCacheSample/Views/Home/Cache.cshtml":::

The following code uses the Set extension method to cache data for a relative time without creating the MemoryCacheEntryOptions object:

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet_set":::

The cached DateTime value remains in the cache while there are requests within the timeout period.

The following code uses xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreate%2A and xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreateAsync%2A to cache data.

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet2" highlight="3-7,14-19":::

The following code calls xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.Get%2A to fetch the cached time:

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet_gct":::

The following code gets or creates a cached item with absolute expiration:

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet99":::

A cached item set with only a sliding expiration is at risk of never expiring. If the cached item is repeatedly accessed within the sliding expiration interval, the item never expires. Combine a sliding expiration with an absolute expiration to guarantee the item expires. The absolute expiration sets an upper bound on how long the item can be cached while still allowing the item to expire earlier if it isn't requested within the sliding expiration interval. If either the sliding expiration interval or the absolute expiration time pass, the item is evicted from the cache.

The following code gets or creates a cached item with both sliding and absolute expiration:

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet9":::

The preceding code guarantees the data will not be cached longer than the absolute time.

xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreate%2A, xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.GetOrCreateAsync%2A, and xref:Microsoft.Extensions.Caching.Memory.CacheExtensions.Get%2A are extension methods in the xref:Microsoft.Extensions.Caching.Memory.CacheExtensions class. These methods extend the capability of xref:Microsoft.Extensions.Caching.Memory.IMemoryCache.

MemoryCacheEntryOptions

The following sample:

  • Sets a sliding expiration time. Requests that access this cached item will reset the sliding expiration clock.
  • Sets the cache priority to xref:Microsoft.Extensions.Caching.Memory.CacheItemPriority.NeverRemove?displayProperty=nameWithType.
  • Sets a xref:Microsoft.Extensions.Caching.Memory.PostEvictionDelegate that will be called after the entry is evicted from the cache. The callback is run on a different thread from the code that removes the item from the cache.

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet_et" highlight="14-21":::

Use SetSize, Size, and SizeLimit to limit cache size

A MemoryCache instance may optionally specify and enforce a size limit. The cache size limit does not have a defined unit of measure because the cache has no mechanism to measure the size of entries. If the cache size limit is set, all entries must specify size. The ASP.NET Core runtime does not limit cache size based on memory pressure. It's up to the developer to limit cache size. The size specified is in units the developer chooses.

For example:

  • If the web app was primarily caching strings, each cache entry size could be the string length.
  • The app could specify the size of all entries as 1, and the size limit is the count of entries.

If xref:Microsoft.Extensions.Caching.Memory.MemoryCacheOptions.SizeLimit isn't set, the cache grows without bound. The ASP.NET Core runtime doesn't trim the cache when system memory is low. Apps must be architected to:

  • Limit cache growth.
  • Call xref:Microsoft.Extensions.Caching.Memory.MemoryCache.Compact%2A or xref:Microsoft.Extensions.Caching.Memory.MemoryCache.Remove%2A when available memory is limited:

The following code creates a unitless fixed size xref:Microsoft.Extensions.Caching.Memory.MemoryCache accessible by dependency injection:

:::code language="csharp" source="memory/samples/3.x/RPcache/Services/MyMemoryCache.cs" id="snippet":::

SizeLimit does not have units. Cached entries must specify size in whatever units they deem most appropriate if the cache size limit has been set. All users of a cache instance should use the same unit system. An entry will not be cached if the sum of the cached entry sizes exceeds the value specified by SizeLimit. If no cache size limit is set, the cache size set on the entry will be ignored.

The following code registers MyMemoryCache with the dependency injection container.

:::code language="csharp" source="memory/samples/3.x/RPcache/Startup.cs" id="snippet":::

MyMemoryCache is created as an independent memory cache for components that are aware of this size limited cache and know how to set cache entry size appropriately.

The following code uses MyMemoryCache:

:::code language="csharp" source="memory/samples/3.x/RPcache/Pages/SetSize.cshtml.cs" id="snippet":::

The size of the cache entry can be set by xref:Microsoft.Extensions.Caching.Memory.MemoryCacheEntryOptions.Size or the xref:Microsoft.Extensions.Caching.Memory.MemoryCacheEntryExtensions.SetSize%2A extension methods:

:::code language="csharp" source="memory/samples/3.x/RPcache/Pages/SetSize.cshtml.cs" id="snippet2" highlight="9,10,14,15":::

MemoryCache.Compact

MemoryCache.Compact attempts to remove the specified percentage of the cache in the following order:

  • All expired items.
  • Items by priority. Lowest priority items are removed first.
  • Least recently used objects.
  • Items with the earliest absolute expiration.
  • Items with the earliest sliding expiration.

Pinned items with priority xref:Microsoft.Extensions.Caching.Memory.CacheItemPriority.NeverRemove are never removed. The following code removes a cache item and calls Compact:

:::code language="csharp" source="memory/samples/3.x/RPcache/Pages/TestCache.cshtml.cs" id="snippet3":::

For more information, see the Compact source on GitHub.

Cache dependencies

The following sample shows how to expire a cache entry if a dependent entry expires. A xref:Microsoft.Extensions.Primitives.CancellationChangeToken is added to the cached item. When Cancel is called on the CancellationTokenSource, both cache entries are evicted.

:::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet_ed":::

Using a xref:System.Threading.CancellationTokenSource allows multiple cache entries to be evicted as a group. With the using pattern in the code above, cache entries created inside the using block will inherit triggers and expiration settings.

Additional notes

  • Expiration doesn't happen in the background. There is no timer that actively scans the cache for expired items. Any activity on the cache (Get, Set, Remove) can trigger a background scan for expired items. A timer on the CancellationTokenSource (xref:System.Threading.CancellationTokenSource.CancelAfter%2A) also removes the entry and triggers a scan for expired items. The following example uses xref:System.Threading.CancellationTokenSource.%23ctor(System.TimeSpan) for the registered token. When this token fires it removes the entry immediately and fires the eviction callbacks:

    :::code language="csharp" source="memory/samples/3.x/WebCacheSample/Controllers/HomeController.cs" id="snippet_ae":::

  • When using a callback to repopulate a cache item:

    • Multiple requests can find the cached key value empty because the callback hasn't completed.
    • This can result in several threads repopulating the cached item.

  • When one cache entry is used to create another, the child copies the parent entry's expiration tokens and time-based expiration settings. The child isn't expired by manual removal or updating of the parent entry.

  • Use xref:Microsoft.Extensions.Caching.Memory.ICacheEntry.PostEvictionCallbacks to set the callbacks that will be fired after the cache entry is evicted from the cache. In the example code, xref:System.Threading.CancellationTokenSource.Dispose?displayProperty=nameWithType is called to release the unmanaged resources used by the CancellationTokenSource. However, the CancellationTokenSource is not disposed immediately because it is still being used by the cache entry. The CancellationToken is passed to MemoryCacheEntryOptions to create a cache entry that expires after a certain time. So Dispose should not be called until the cache entry is removed or expired. The example code calls the xref:Microsoft.Extensions.Caching.Memory.MemoryCacheEntryExtensions.RegisterPostEvictionCallback%2A method to register a callback that will be invoked when the cache entry is evicted, and it disposes the CancellationTokenSource in that callback.

  • For most apps, IMemoryCache is enabled. For example, calling AddMvc, AddControllersWithViews, AddRazorPages, AddMvcCore().AddRazorViewEngine, and many other Add{Service} methods in ConfigureServices, enables IMemoryCache. For apps that are not calling one of the preceding Add{Service} methods, it may be necessary to call xref:Microsoft.Extensions.DependencyInjection.MemoryCacheServiceCollectionExtensions.AddMemoryCache%2A in ConfigureServices.

Background cache update

Use a background service such as xref:Microsoft.Extensions.Hosting.IHostedService to update the cache. The background service can recompute the entries and then assign them to the cache only when they’re ready.

Additional resources

  • xref:performance/caching/distributed
  • xref:fundamentals/change-tokens
  • xref:performance/caching/response
  • xref:performance/caching/middleware
  • xref:mvc/views/tag-helpers/builtin-th/cache-tag-helper
  • xref:mvc/views/tag-helpers/builtin-th/distributed-cache-tag-helper

:::moniker-end