This enumeration is used by the SetRevalidation( ) method of the HttpCachePolicy class, which programmatically forces the revalidation of a page. If you use ProxyCaches with this method, the page will be dropped from all shared caches, but potentially left in the client's local cache. (Technically, this sets the "Cache-Control: proxy-revalidate" HTTP header.) If you use AllCaches, the page will be dropped from all caches. (Technically, this sets the "Cache-Control: must-revalidate" HTTP header.)