The HttpCachePolicy.AddValidationCallback(HttpCacheValidateHandler, object) method provides a mechanism to check the response programmatically in the cache before the response is returned to the client by the output cache.

Before the response is served from the Web server cache, all registered handlers are queried to ensure resource validity. If any handler sets a flag indicating that the cached response is not valid, the entry is marked as not valid and expelled from the cache. In this case, as well as when any handler indicates that the cached response should be ignored for this request, the request is then handled as if it were a cache miss.

HttpCachePolicy.AddValidationCallback(HttpCacheValidateHandler, object) is introduced in the .NET Framework version 3.5. For more information, see The .NET Framework 3.5 Architecture.

Namespace: System.Web
Assembly: System.Web (in System.Web.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0