Chapter 22: System.Runtime.Caching.MemoryCache (ObjectCache)

Section 22.1: Adding Item to Cache (Set)

Set function inserts a cache entry into the cache by using a CacheItem instance to supply the key and value for the cache entry.

This function Overrides ObjectCache.Set(CacheItem, CacheItemPolicy)

private static bool SetToCache()

{

string key = "Cache_Key"; string value = "Cache_Value";

//Get a reference to the default MemoryCache instance. var cacheContainer = MemoryCache.Default;

var policy = new CacheItemPolicy()

{

AbsoluteExpiration = DateTimeOffset.Now.AddMinutes(DEFAULT_CACHE_EXPIRATION_MINUTES)

};

var itemToCache = new CacheItem(key, value); //Value is of type object. cacheContainer.Set(itemToCache, policy);

}

Section 22.2: System.Runtime.Caching.MemoryCache (ObjectCache)

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);

}

}