CacheItemPolicy

CacheItemPolicy is a class in the Microsoft .NET Framework that allows developers to define expiration and eviction policies for cache entries. It is part of the System.Runtime.Caching namespace, introduced to provide a more flexible and modern caching API compared to the older System.Web.Caching.

The CacheItemPolicy object can be used to specify how long an item should remain in the cache before it expires. This is achieved through properties like AbsoluteExpiration and SlidingExpiration. AbsoluteExpiration sets a fixed date and time after which the cache item will be removed. SlidingExpiration, on the other hand, defines a duration relative to the last access time of the cache item. If the item is not accessed within this duration, it will expire.

In addition to expiration, CacheItemPolicy also supports change monitors. Change monitors allow the cache to be invalidated when an external condition changes, such as a file being modified or an entry in a database being updated. By creating and attaching a change monitor to the CacheItemPolicy, developers can ensure that their cached data remains consistent with the underlying data source.

When adding an item to the cache using the MemoryCache class, a CacheItemPolicy object can be provided to customize its behavior. If no policy is specified, a default policy with no expiration is used, meaning items will remain in the cache indefinitely until memory pressure triggers their eviction. Understanding and utilizing CacheItemPolicy is crucial for effective cache management, helping to balance performance gains with data freshness and memory usage.