There is no out of the box support for retrieving all Keys of the CacheManager.
If you really need this behavior you could try to rethink your "key" design. E.g. use multiple CacheManager instances to store specific keys.
Based on your code it looks like you are trying to cache some information on a per user basis. To do that you could use dynamic cache managers. See
this stackoverflow question for more information on how to do that. Note there is no automatic way to free unused caches so there could be memory implications with that approach.
Another option would be to extend the block and implement your own custom CacheManager to provide the functionality that you wish. It should be fairly straight forward to reuse the current CacheManager implementation (see the source code) to provide
the needed properties. The Cache object actually already has a property CurrentCacheState that returns a Hashtable which will allow you to get the Keys so it would just be a matter of surfacing that information on the CacheManager.
Enterprise Library support engineer