Static class to simplify work with ASP.NET Cache.

CacheHelper.cs

    public static class CacheHelper
    {
        /// <summary>
        /// Returns cache value or default(T) if no value in cache
        /// </summary>
        /// <typeparam name="T">Type of cached value</typeparam>
        /// <param name="key">Cache key for cached value</param>
        /// <returns>Cached value</returns>
        public static T Get<T>(string key)
        {
            var value = default(T);
            if (Exists(key))
            {
                value = (T)HttpRuntime.Cache[key];
            }
            return value;
        }

        /// <summary>
        /// Returns value from cache if it exists in cache by provided key.
        /// Returns value created by creator and adds this value to cache if value doesn't exist in cache by provided key.
        /// </summary>
        /// <typeparam name="T">Type of value to cache</typeparam>
        /// <param name="key">Unique cache key for cacheable value</param>
        /// <param name="creator">Function which creates value for caching</param>
        /// <param name="cacheAdder">Action which adds value to cache</param>
        /// <returns>Cached value</returns>
        public static T GetOrCacheValue<T>(string key, Func<T> creator, Action<string, object> cacheAdder)
        {
            var value = Get<T>(key);

            if (EqualityComparer<T>.Default.Equals(value, default(T)))
            {
                var lockObject = lockObjects.GetOrAdd(key, new object());
                lock (lockObject)
                {
                    value = Get<T>(key);

                    if (EqualityComparer<T>.Default.Equals(value, default(T)))
                    {
                        value = creator();
                        cacheAdder(key, value);
                    }
                }
            }

            return value;
        }

        private static readonly ConcurrentDictionary<string, object> lockObjects = new ConcurrentDictionary<string, object>();

        /// <summary>
        /// Check for item in cache
        /// </summary>
        /// <param name="key">Name of cached item</param>
        /// <returns></returns>
        public static bool Exists(string key)
        {
            return HttpRuntime.Cache[key] != null;
        }
    }