Get Absolute Expiration event from ObjectCache

Question

I'm using an ObjectCache object as MemoryCache.Default (System.Runtime.Caching) and my policy contains AbsoluteExpiration.

for example:

ObjectCache cache = MemoryCache.Default
cahce.Add(key, reading, new CacheItemPolicy { AbsoluteExpiration = DateTimeOffset.Now.AddSeconds(20)});

I would like to save the objects before it's being removed.

Is it possible to catch the event of expiration, before item removed from cache?

Answer 1

When you add an Entry in MemoryCache with Add function, you can add CacheItemPolicy.

This class have this fields:

     private DateTimeOffset _absExpiry;
        private TimeSpan _sldExpiry;
        private Collection<ChangeMonitor> _changeMonitors;
        private CacheItemPriority _priority;
        private CacheEntryRemovedCallback _removedCallback;
        private CacheEntryUpdateCallback _updateCallback;

What you need is _removedCallback.

Source code: here and here.