I downloaded and installed Postsharp the essentials version which according to the matrix on their website includes caching.
I added it to my project by right clicking and selecting the Add Postsharp option.
When I go into my project to play with testing and I type:
using PostSharp.Patterns
Patterns is not an option for me, I have Aspects, Collections, Constraints... but no Patterns.
Am I missing a reference, is this a license issue?
PostSharp is split into multiple NuGet packages. Selecting "Add PostSharp to project" only installs the core package (PostSharp). In your case, you need to install PostSharp.Patterns.Caching. Please note that you will also need to specify the caching backend, see the documentation on caching.