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Area: Episerver CMS
Applies to versions: 10 and higher
Other versions:

Object caching

The IObjectInstanceCache and ISynchronizedObjectInstanceCache interfaces expose the built-in cache system with custom dependency and eviction policies. Episerver CMS and Commerce use this to cache both content and system data, and it can be used to cache custom data. The ISynchronizedObjectInstanceCache interface synchronizes cache removal among servers in a load-balanced environment using the event system.

Note: If you were using the CacheManager class in CMS, you should take a dependency on ISynchronizedObjectInstanceCache instead, because the new interface provides the same functionality. The IObjectInstanceCache supersedes IRuntimeCache (that was previously only used by CMS) because it supports different cache implementations by abstracting the CacheDependency class and other things. The underlying default implementation of IObjectInstanceCache still relies on HttpRuntime.Cache.

CacheEvictionPolicy

Use the CacheEvictionPolicy class for object caching, because it is de-coupled from any specific cache implementation. CacheEvictionPolicy is immutable so you can re-use existing instances of the class. (The CacheDependency class is tightly coupled to the HttpRuntime implementation and if you want to have a custom cache implementation you cannot rely on CacheDependency.) The following example shows how to use CacheEvictionPolicy.

public void AddToCache(string key, object val)
{
    // If you don't care about specific cache management, use CacheEvictionPolicy.Empty
    _cache.Insert(key, val, CacheEvictionPolicy.Empty);

    // To enable sliding expiration for 10s, depending on "otherKey"
    _cache.Insert(key, val, new CacheEvictionPolicy(
        new string[] { "otherKey" }, // Cache key dependency
        new TimeSpan(0, 0, 10),      // Always a timespan for timeouts
        CacheTimeoutType.Sliding);
}

Master keys

When you need to define a common dependency for cached data, create a master dependency (or master key) with CacheEvictionPolicy, which automatically adds a list of key names to the cache as regular cache entries. By doing so, you do not need to add code to conditionally add these entries before you insert specific data into the cache.

In the following example, the difference between the cache key dependency and the master key dependency is that if there is no otherKey in the cache then the data is not inserted. If there is no entry with MasterKey, then it adds a dummy value with the given key, thus allowing the data to be inserted successfully.

public void AddToCacheWithMasterDependency(string key, object val)
{
    // To enable absolute expiration for 5 minutes, depending on "otherKey" and master key dependency to "MasterKey"
    _cache.Insert(key, val, new CacheEvictionPolicy(
        null,                         // No file dependencies
        new string[] { "otherKey" },  // Cache key dependency
        new string[] { "MasterKey" }, // Master key dependency
        new TimeSpan(0, 5, 0),        // Always a timespan for timeouts
        CacheTimeoutType.Absolute);
}
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Last updated: Apr 08, 2019