I realize this question is old, but in the interest of helping anyone who finds this via search, its worth noting that .net v4 includes a new general purpose cache for this type of scenario. It’s in the System.Runtime.Caching namespace:
https://msdn.microsoft.com/en-us/library/dd997357(v=vs.110).aspx
The static reference to the default cache instance is: MemoryCache.Default