MemoryCacheHelper

using System;
using System.Configuration;
using System.Linq;
using System.Runtime.Caching;

namespace CBW.Cache
{
    public class MemoryCacheHelper
    {
        public object GetValue(string key)
        {
            MemoryCache memoryCache = MemoryCache.Default;

            return memoryCache.Get(key);
        }

        public bool Add(string key, object value, DateTimeOffset absExpiration)
        {
            MemoryCache memoryCache = MemoryCache.Default;

            return memoryCache.Add(key, value, absExpiration);
        }

        public static void Delete(string key)
        {
            MemoryCache memoryCache = MemoryCache.Default;

            if (memoryCache.Any(kv => kv.Key.StartsWith(key)))
            {
                var entries = memoryCache.Where(kv => kv.Key.StartsWith(key)).ToList();

                foreach (var entry in entries)
                {
                    memoryCache.Remove(entry.Key);
                }
            }
        }

        public static T GetOrAddValue<T>(string cacheKey, Func<T> getValueFunction, string cacheDurationConfigKey)
            where T : class
        {
            var cacheDuration = GetCacheDuration(cacheDurationConfigKey);

            if (cacheDuration > 0)
            {
                return GetOrAddValue(cacheKey, getValueFunction, item => DateTime.Now.AddSeconds(cacheDuration));
            }

            return getValueFunction();
        }

        public static T GetOrAddValue<T>(string cacheKey, Func<T> getValueFunction, Func<T, DateTime> cacheDurationFunction)
            where T : class
        {
            var cache = new MemoryCacheHelper();
            var itemToBeCached = cache.GetValue(cacheKey) as T;

            if (itemToBeCached != null)
            {
                return itemToBeCached;
            }

            itemToBeCached = getValueFunction();

            if (itemToBeCached == null)
            {
                return null;
            }

            var cacheDuration = cacheDurationFunction(itemToBeCached);

            cache.Add(cacheKey, itemToBeCached, cacheDuration);

            return itemToBeCached;
        }

        private static int GetCacheDuration(string cacheDurationConfigKey)
        {
            var cacheDurationText = ConfigurationManager.AppSettings[cacheDurationConfigKey];
            int cacheDuration;

            if (int.TryParse(cacheDurationText, out cacheDuration))
            {
                return cacheDuration;
            }

            return 0;
        }
    }
}