I'm having problems getting AppendHeader to work properly if I am also using an authorize filter. I'm using an actionfilter for my AJAX actions that applies Expires, Last-Modified, Cache-Control and Pragma (though while testing I have tried including it in the action method itself with no change in results).

If I don't have an authorize filter the headers work fine. Once I add the filter the headers I tried to add get stripped.

The headers I want to add

Response.AppendHeader("Expires", "Sun, 19 Nov 1978 05:00:00 GMT");
Response.AppendHeader("Last-Modified", String.Format("{0:r}", DateTime.Now));
Response.AppendHeader("Cache-Control", "no-store, no-cache, must-revalidate");
Response.AppendHeader("Cache-Control", "post-check=0, pre-check=0");
Response.AppendHeader("Pragma", "no-cache");

An example of the headers from a correct page:

Server ASP.NET Development Server/9.0.0.0
Date    Mon, 14 Jun 2010 17:22:24 GMT
X-AspNet-Version    2.0.50727
X-AspNetMvc-Version 2.0
Pragma  no-cache
Expires Sun, 19 Nov 1978 05:00:00 GMT
Last-Modified   Mon, 14 Jun 2010 18:22:24 GMT
Cache-Control   no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Content-Type    text/html; charset=utf-8
Content-Length  352
Connection  Close

And from an incorrect page:

Server  ASP.NET Development Server/9.0.0.0
Date    Mon, 14 Jun 2010 17:27:34 GMT
X-AspNet-Version    2.0.50727
X-AspNetMvc-Version 2.0
Pragma  no-cache, no-cache
Cache-Control   private, s-maxage=0
Content-Type    text/html; charset=utf-8
Content-Length  4937
Connection  Close