Eyes wide open - Correct Caching is always hard

The code is below. Note that the MemoryCache is a singleton, but within the process. It is not (yet) a DistributedCache. Also note that Caching is Complex(tm) and that thousands of pages have been written about caching by smart people. This is a blog post as part of a series, so use your head and do your research. Don't take anyone's word for it.