Generic cache wrapper for the asp.net HttpCache

I seem to search for this little nugget every now and again without finding it on the net, so here it is. I really can’t take credit for it, I think it was the bentster who wrote it first time I saw it, but not really sure…

What to cache

Typical usage is data for populating dropdown lists with options which doesn’t change too often, like once a day. This is probably the most frequently used data from a database, so making the app hit the db only once per day(per list) can really make a difference if you have some load.

How to cache

The ASP.NET HttpCache is really simple and can be used for all types of .net applications(I have used it mainly in web-apps, but also in a wcf-project). The reason for having the caching logic isolated in a class is it’s really easy to get the locking wrong.

Le code

There really isn’t much to it, except for the double checking.

public class Cache<T> where T : class
{
	public T Get(object lockObject, string key, Func<T> getFunction, int hoursToCache)
	{
		var result = HttpRunTime.Cache.Get(key);
		if (result == null)
		{
			lock (lockObject)
			{
				result = HttpRunTime.Cache.Get(key);
				if (result == null)
				{
					result = getFunction();
					HttpRunTime.Cache.Insert(key, result, null, DateTime.UtcNow.AddHours(hoursToCache), Cache.NoSlidingExpiration);
				}
			}
		}
		return (T) result;
	}
}

Your only concern using it is which lock-object to give it. I usually make a “retriever” class for each list I need, and give the cache the typeof(MyListRetriever) to use for locking.

TODO: usage example and lambda with param