The current cache policy and the presence of the requested resource in the cache determine whether a response can be retrieved from the cache. Using cached responses usually improves application performance, but there is a risk that the response in the cache does not match the response on the server.

Default cache policy can be specified in the Machine.config configuration file or by setting the HttpWebRequest.DefaultCachePolicy property for requests that use the Hypertext Transfer Protocol (HTTP) or Secure Hypertext Transfer Protocol (HTTPS) URI scheme.

A copy of a resource is only added to the cache if the response stream for the resource is retrieved and read to the end of the stream. So another request for the same resource could use a cached copy, depending on the cache policy level for this request.