How to get ICacheEntry from Microsoft.Extensions.Caching.Memory.MemoryCache

Question

In my application I use MemoryCache and I wanted to add a functionality to it. When I read a value from the cache I want to check against its expiration date and if it's soon, I want to run a refresh (which takes long) for this key in the background.

To achieve this I need to get ICacheEntry which has the info about the expiration date, but there is no way to access it through IMemoryCache interface which I use. So I decided to derive from it and add a method to get ICacheEntry. The problem is that EntriesCollection in MemoryCache is private instead of protected.

Is there any other way to get cache entry (not just value of cached entry) using this library? Or should I use some other library to achieve what I need?

Answer 1

var cacheEntriesCollectionDefinition = typeof(MemoryCache).GetProperty("EntriesCollection", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);

// Populate the definition with your IMemoryCache instance.  
// It needs to be cast as a dynamic, otherwise you can't
// loop through it due to it being a collection of objects.
var cacheEntriesCollection = cacheEntriesCollectionDefinition.GetValue(this) as dynamic;

// Define a new list we'll be adding the cache entries too
List<Microsoft.Extensions.Caching.Memory.ICacheEntry> cacheCollectionValues = new List<Microsoft.Extensions.Caching.Memory.ICacheEntry>();

foreach (var cacheItem in cacheEntriesCollection)
{
    // Get the "Value" from the key/value pair which contains the cache entry   
    Microsoft.Extensions.Caching.Memory.ICacheEntry cacheItemValue = cacheItem.GetType().GetProperty("Value").GetValue(cacheItem, null);

    // Add the cache entry to the list
    cacheCollectionValues.Add(cacheItemValue);
}

// You can now loop through the cacheCollectionValues list created above however you like.`