OnCacheExpiration event

[felipedrumond]

Is there any way to configure an event to be run when the cache expires?

My scenario is the following: I have a web api that serves a list of banners. I want to increase their 'views' property every time I display every banner. Instead of updating the repository every time, it's better to update that property in the cached list and update the repository only when the cache expires.

[felipedrumond]

I managed to do it, and I'll write a piece of code for others just as an example

-- creates my policy

CacheItemPolicy policyWithExpirationCallBack = new CacheItemPolicy
            {
                AbsoluteExpiration = DateTime.Now.AddMinutes(1),
                RemovedCallback = OnCacheExpired 
            };

-- gets an existing list of banners. If that list does not exist yet, add one with my policy

            List<Banner> banners = cache.GetOrAdd(
                "yourCacheName",
                () =>
                {
                    return _bannerRepository.ReadAll();
                },
                policyWithExpirationCallBack);

            return banners;

-- method to be called when my cache expires

private void OnCacheExpired(CacheEntryRemovedArguments arguments)
{
   // if you need the last version of your cached data, you can get it from arguments.CacheItem.Value

   var lastVersionOfBanners = (List<Banner>)arguments.CacheItem.Value;
}

[alastairtree]

Thanks for this, I have updated the docs with an example based on yours: https://github.com/alastairtree/LazyCache/wiki/1.0-LazyCache-API-documentation#custom-cache-policies