public PubSubCache(IPubSub pubSubProvider, string cacheInstanceKey = null)
{
this.pubSub = pubSubProvider;
this.memoryCacheInstance = new MemoryCache(this.pubSub.GetType().Name + (cacheInstanceKey ?? ""));
this.subscription = pubSub.CreateEmptySubscription();
this.filter = new InvalidationFilter();
this.subscription.OnMessage += filter.OnMessageReceived;
}