Not sure if this is the right place, but I would like to recommend removing the default result from the cache provider extension:

public static T GetCacheItem<T>(this ICacheProvider provider, string cacheKey)
        {
            var result = provider.GetCacheItem(cacheKey);
            if (result == null)
            {
                return default(T);
            }
            return result.TryConvertTo<T>().Result;
        }

Notice how the cache will return a default if the get does not return a result. This can create unknown results on behalf of consumers of this service. They may think they have gotten the correct object, but in fact have gotten a default value. The consume should make a decision what to do in the event of a null result. The fix here is to change return default(T) to return null.