Have you ever created a new email message with the main objective being to send someone an attachment and then forget to attach said attachment?  Apparently I did something similar to that in my last post.  At the time of the post, I couldn't get the attach file method to work so I intended to add it later, but I didn't.  That makes me a sad panda :(

I've been using a variant of this caching method with good results for quite some time.  So to make amends I'm going to post an updated version AND a proper sample solution.  And this time, I will remember to attach it.

using System;
using System.Reflection;
using System.Web;
using System.Web.Caching;
using log4net;

namespace BDI.Caching
{
	public class CacheHelper
	{
		private static readonly ILog log =
			LogManager.GetLogger(
				MethodBase.GetCurrentMethod().DeclaringType );

		private static readonly bool isInfoEnabled = log.IsInfoEnabled;
		private static readonly Cache cache = HttpRuntime.Cache;
		private CacheHelper() {}

		public static T GetFromCache<T>(
			string key,
			int cacheTimeInMinutes,
			CacheExpiration cacheExpiration,
			Func<T> retrieveMethod ) where T : class
		{

            var target = cache[key] as T;

            if ( target == null )
            {
                if (isInfoEnabled)
                    log.Info("Cache miss for key:" + key + "  type:" + typeof (T));

                target = retrieveMethod();

                var absoluteExpiration = Cache.NoAbsoluteExpiration;
                var slidingExpiration = Cache.NoSlidingExpiration;

                switch (cacheExpiration)
                {
                    case CacheExpiration.Sliding:
                        slidingExpiration = new TimeSpan(0, cacheTimeInMinutes, 0);
                        break;
                    case CacheExpiration.Absolute:
                        absoluteExpiration = DateTime.Now.AddMinutes(cacheTimeInMinutes);
                        break;
                }

                cache.Insert(key, target, null, absoluteExpiration, 
                    slidingExpiration, CacheItemPriority.Normal, OnRemove);

            }
            else
            {
                if ( isInfoEnabled )
                    log.Info( "Cache hit for key:" + key + "  type:" + typeof( T ) );
            }

		    return target;
		}

		public static void OnRemove( string key, object cacheItem, CacheItemRemovedReason reason )
		{
			if( isInfoEnabled )
				log.Info( "Object removed from cache: Key-" + key + ": Reason-" + reason );
		}

		public static void RemoveFromCache( string key )
		{
			if( isInfoEnabled )
				log.Info( "Object manually removed from cache: Key-" + key );

			cache.Remove( key );
		}
	}
}