I'm having some trouble sorting out image caching for JPEGs that are
served through an IHttpModule.

A quirk of the site I'm working on at the moment is that product images
are served via a third-party image hosting provider (Scene7, who have
been very helpful and so deserve a credit). In order to save having to
reference the URI stem all over our code, I wrote an IHttpModule that
parses all requests on the basis of:

HttpContext context = ((HttpApplication) sender).Context;
HttpRequest request = context.Request;

Regex r = new Regex(
@"/images/products/(?<sku>[A-Z0-9-]+)_(?<size>\d)\.jpg",
RegexOptions.Compiled | RegexOptions.IgnoreCase);
Match m = r.Match(request.RawUrl);

if (m.Success && request.HttpMethod == "GET")
{
// Handle the Scene7-specific stuff
}
else
{
// Set cacheability
}

Before I was doing anything in this else clause, Fiddler
(www.fiddlertool.com) was showing me that the following headers were
being sent with all non-Scene7 JPEGs:

Pragma: no-cache
Cache-Control: no-cache
Pragma: no-cache
Expires: -1

Now, if I add the following two lines to my else clause:

HttpCachePolicy cache = context.Response.Cache;
cache.SetAllowResponseInBrowserHistory(true);

it gets rid of the "Expires: -1" header. Adding any / all of the
following, though, won't shift the Pragma: and Cache-Control: headers
-- they all seem to have no effect on my actual HTTP transaction, so
it's still not being cached properly:

cache.SetCacheability(HttpCacheability.Public);
cache.SetMaxAge(new TimeSpan(30, 0, 0, 0));
cache.SetExpires(DateTime.Now.AddDays(30));
cache.SetLastModifiedFromFileDependencies();
cache.SetValidUntilExpires(true);

Does anyone have any experience with setting HttpCachePolicy properties
from within an IHttpModule? Am I missing something really obvious?

If people could try to remember to cc: me on replies, as well as
sending them to this newsgroup, as I don't always remember to check
Usenet as often as I'd like.

Thanks everyone!


Owen
--
Owen Blacker
Senior Software Developer

Wheel: insight | thinking | creativity

owen.blacker (AT) wheel (DOT) co.uk www.wheel.co.uk