Assembly: System.Web (in system.web.dll)
The name of the HTTP header to add to the output stream.
The string to append to the header.
The header is appended after the HTTP headers have been sent.
If you use the AppendHeader method to send cache-specific headers and at the same time use the cache object model (Cache) to set cache policy, HTTP response headers pertaining to caching (Cache-Control, Expires, Last-Modified, Pragma, and Vary) might be deleted when the cache object model is used. This behavior enables ASP.NET to maintain the most restrictive settings. For example, consider a page that includes user controls. If those controls have conflicting cache policies, the most restrictive cache policy will be used. If one user control sets the header " Cache-Control: Public " and another sets the more restrictive header " Cache-Control: Private " via calls to SetCacheability, then the " Cache-Control: Private " header will be sent with the response.