Specifies whether the ASP.NET cache should ignore HTTP Cache-Control headers sent by the client that invalidate the cache.
The HttpCachePolicy.SetValidUntilExpires(bool) method is set to true automatically when the high-level <%@ OutputCache … %> page directive is used.
This method is provided because some browsers, when refreshing a page view, send HTTP cache invalidation headers to the Web server and evict the page from the cache. When the validUntilExpires parameter is true, ASP.NET ignores cache invalidation headers and the page remains in the cache until it expires.
HttpCachePolicy.SetValidUntilExpires(bool) is introduced in the .NET Framework version 3.5. For more information, see The .NET Framework 3.5 Architecture.