.NET Framework System.Runtime.Caching.MemoryCache (ObjectCache)


Example

This function gets existing item form cache, and if the item don't exist in cache, it will fetch item based on the valueFetchFactory function.

    public static TValue GetExistingOrAdd<TValue>(string key, double minutesForExpiration, Func<TValue> valueFetchFactory)
    {            
        try
        {
            //The Lazy class provides Lazy initialization which will evaluate 
            //the valueFetchFactory only if item is not in the cache.
            var newValue = new Lazy<TValue>(valueFetchFactory);

            //Setup the cache policy if item will be saved back to cache.
            CacheItemPolicy policy = new CacheItemPolicy()
            {
                AbsoluteExpiration = DateTimeOffset.Now.AddMinutes(minutesForExpiration)
            };

            //returns existing item form cache or add the new value if it does not exist.
            var cachedItem = _cacheContainer.AddOrGetExisting(key, newValue, policy) as Lazy<TValue>;

            return (cachedItem ?? newValue).Value;
        }
        catch (Exception excep)
        {
            return default(TValue);
        }
    }