CSHARP

ASP.NET Core set update clear cache from IMemoryCache (set by Set method of CacheExtensions class)

serviceCollection.AddSingleton<IMyCache, MyMemoryCache>();

ASP.NET Core set update clear cache from IMemoryCache (set by Set method of CacheExtensions class)

Internally it uses IMemoryCache.
Use case is exactly the same with 2 additional features:

Clear all items from memory cache
Iterate through all key/value pairs
You have to register singleton:

serviceCollection.AddSingleton<IMyCache, MyMemoryCache>();
Use case:

public MyController(IMyCache cache)
{
    this._cache = cache;
}

[HttpPut]
public IActionResult ClearCache()
{
    this._cache.Clear();
    return new JsonResult(true);
}

[HttpGet]
public IActionResult ListCache()
{
    var result = this._cache.Select(t => new
    {
        Key = t.Key,
        Value = t.Value
    }).ToArray();
    return new JsonResult(result);
}

ASP.NET Core set update clear cache from IMemoryCache (set by Set method of CacheExtensions class)

serviceCollection.AddSingleton<IMyCache, MyMemoryCache>();

public interface IMyCache : IEnumerable<KeyValuePair<object, object>>, IMemoryCache
{
    /// <summary>
    /// Clears all cache entries.
    /// </summary>
    void Clear();
}

public class MyMemoryCache : IMyCache
{
    private readonly IMemoryCache _memoryCache;
    private readonly ConcurrentDictionary<object, ICacheEntry> _cacheEntries = new ConcurrentDictionary<object, ICacheEntry>();

    public MyMemoryCache(IMemoryCache memoryCache)
    {
        this._memoryCache = memoryCache;
    }

    public void Dispose()
    {
        this._memoryCache.Dispose();
    }

    private void PostEvictionCallback(object key, object value, EvictionReason reason, object state)
    {
        if (reason != EvictionReason.Replaced)
            this._cacheEntries.TryRemove(key, out var _);
    }

    /// <inheritdoc cref="IMemoryCache.TryGetValue"/>
    public bool TryGetValue(object key, out object value)
    {
        return this._memoryCache.TryGetValue(key, out value);
    }

    /// <summary>
    /// Create or overwrite an entry in the cache and add key to Dictionary.
    /// </summary>
    /// <param name="key">An object identifying the entry.</param>
    /// <returns>The newly created <see cref="T:Microsoft.Extensions.Caching.Memory.ICacheEntry" /> instance.</returns>
    public ICacheEntry CreateEntry(object key)
    {
        var entry = this._memoryCache.CreateEntry(key);
        entry.RegisterPostEvictionCallback(this.PostEvictionCallback);
        this._cacheEntries.AddOrUpdate(key, entry, (o, cacheEntry) =>
        {
            cacheEntry.Value = entry;
            return cacheEntry;
        });
        return entry;
    }

    /// <inheritdoc cref="IMemoryCache.Remove"/>
    public void Remove(object key)
    {
        this._memoryCache.Remove(key);
    }

    /// <inheritdoc cref="IMyCache.Clear"/>
    public void Clear()
    {
        foreach (var cacheEntry in this._cacheEntries.Keys.ToList())
            this._memoryCache.Remove(cacheEntry);
    }

    public IEnumerator<KeyValuePair<object, object>> GetEnumerator()
    {
        return this._cacheEntries.Select(pair => new KeyValuePair<object, object>(pair.Key, pair.Value.Value)).GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return this.GetEnumerator();
    }

    /// <summary>
    /// Gets keys of all items in MemoryCache.
    /// </summary>
    public IEnumerator<object> Keys => this._cacheEntries.Keys.GetEnumerator();
}

public static class MyMemoryCacheExtensions
{
    public static T Set<T>(this IMyCache cache, object key, T value)
    {
        var entry = cache.CreateEntry(key);
        entry.Value = value;
        entry.Dispose();

        return value;
    }

    public static T Set<T>(this IMyCache cache, object key, T value, CacheItemPriority priority)
    {
        var entry = cache.CreateEntry(key);
        entry.Priority = priority;
        entry.Value = value;
        entry.Dispose();

        return value;
    }

    public static T Set<T>(this IMyCache cache, object key, T value, DateTimeOffset absoluteExpiration)
    {
        var entry = cache.CreateEntry(key);
        entry.AbsoluteExpiration = absoluteExpiration;
        entry.Value = value;
        entry.Dispose();

        return value;
    }

    public static T Set<T>(this IMyCache cache, object key, T value, TimeSpan absoluteExpirationRelativeToNow)
    {
        var entry = cache.CreateEntry(key);
        entry.AbsoluteExpirationRelativeToNow = absoluteExpirationRelativeToNow;
        entry.Value = value;
        entry.Dispose();

        return value;
    }

    public static T Set<T>(this IMyCache cache, object key, T value, MemoryCacheEntryOptions options)
    {
        using (var entry = cache.CreateEntry(key))
        {
            if (options != null)
                entry.SetOptions(options);

            entry.Value = value;
        }

        return value;
    }

    public static TItem GetOrCreate<TItem>(this IMyCache cache, object key, Func<ICacheEntry, TItem> factory)
    {
        if (!cache.TryGetValue(key, out var result))
        {
            var entry = cache.CreateEntry(key);
            result = factory(entry);
            entry.SetValue(result);
            entry.Dispose();
        }

        return (TItem)result;
    }

    public static async Task<TItem> GetOrCreateAsync<TItem>(this IMyCache cache, object key, Func<ICacheEntry, Task<TItem>> factory)
    {
        if (!cache.TryGetValue(key, out object result))
        {
            var entry = cache.CreateEntry(key);
            result = await factory(entry);
            entry.SetValue(result);
            entry.Dispose();
        }

        return (TItem)result;
    }
}