You should always be doing this consistently with the best practices listed below. You shouldn't be using HttpRuntime.Cache or HttpContext.Current.Cache directly. Instead, you should always be accessing it via the AppCaches cache helper (Umbraco.Cms.Core.Cache
).
The AppCaches
which can be found in namespace Umbraco.Cms.Core.Cache
contains types of cache: Runtime Cache, Request Cache and Isolated Caches.
Runtime Cache is the most commonly used and is synonymous with HttpRuntime.Cache. Request cache is cache that exists only for the current request. This is synonymous with HttpContext.Current.Items and isolated caches. These are used by for example repositories, to ensure that each cached entity type has its own cache. When they have their own cache, lookups are fast and the repository does not need to search through all keys on a global scale.
If you wish to use the AppCaches in a class, you need to use Dependency Injection (DI) in your constructor: