HttpCachePolicy.AppendCacheExtension Method
Assembly: System.Web (in system.web.dll)
If the browser does not recognize cache control directives or extensions, the browser must ignore the unrecognized terms. For more information, see RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1, available on the World Wide Web Consortium (W3C) Web site.
The following code example demonstrates the use of a cache-control extension supported by Internet Explorer. The server is indicating to the browser that the content will not change for one hour (pre-check=3600) and instructs it to retrieve the content directly from the local cache. However, if the content is modified by the server and the page is requested by the user within a fifteen-minute (post-check= 900) to one-hour period, the browser displays the information found in the local cache but also performs a background check and optional fetch of the new content on the server.
get_Response().get_Cache().
AppendCacheExtension("post-check=900,pre-check=3600");
Response.Cache.AppendCacheExtension("post-check=900,pre-check=3600")