How to specify HTTP expiration header? (ASP.NET MVC+IIS)

Question

I am already using output caching in my ASP.NET MVC application.

Page speed tells me to specify HTTP cache expiration for css and images in the response header.

I know that the Response object contains some properties that control cache expiration. I know that these properties can be used to control HTTP caching for response that I am serving from my code:

Response.Expires
Response.ExpiresAbsolute
Response.CacheControl

or alternatively

Response.AddHeader("Expires", "Thu, 01 Dec 1994 16:00:00 GMT");

The question is how do I set the Expires header for resources that are served automatically, e.g. images, css and such?

IIS 7...but I may not have access to all settings in IIS, this site is hosted — Marek, Apr 09 '10 at 15:47
You can set it in IIS: https://blogs.msdn.microsoft.com/rakkimk/2007/07/09/iis7-how-to-enable-content-expiration/ — Tyler S. Loeper, Apr 05 '18 at 16:58

score 79 · Accepted Answer · answered Apr 09 '10 at 15:50

79

Found it:

I need to specify client cache for static content (in web.config).

<configuration>
  <system.webServer>
    <staticContent>
      <clientCache cacheControlCustom="public" 
      cacheControlMaxAge="12:00:00" cacheControlMode="UseMaxAge" />
    </staticContent>
   </system.webServer>
</configuration>

from http://www.iis.net/ConfigReference/system.webServer/staticContent/clientCache

answered Apr 09 '10 at 15:50

Marek

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how is this different than setting a far future expire date in IIS ?? – leora Mar 19 '11 at 02:54
3

not sure if there is any difference - feel free to check the differences in HTTP traffic :) The mentioned approach has an advantage that it is possible to alter the caching behavior without configuring IIS (e.g. on shared hosting) – Marek Mar 21 '11 at 10:27
What if, one of the image changes before the cache expiry date. How do we initial the 302 request for that image? – sameer Oct 28 '14 at 17:30
1

@sameer if it's a different image, use a different name, or use a cache-buster (querystring with date of file) – Tracker1 Feb 10 '15 at 17:17
Also, for anyone curious, when you hit refresh on the browser, it will do an if-modified-since request for each file... if you navigate, you'll see the cache response. – Tracker1 Feb 10 '15 at 17:32
i tried this but i have a issue [here](http://stackoverflow.com/questions/35704618/asp-mvc-expire-headers-not-set-for-static-contents) is my question, expire header is not set – Shaiju T Mar 12 '16 at 11:54

score 31 · Answer 2 · answered Jun 22 '11 at 16:04

31

If you want to do it from code for a resource that you're returning (ie. not a static file being served from IIS), you're better off using Response.Cache:

Response.Cache.SetExpires(DateTime.Now.AddYears(1));
Response.Cache.SetCacheability(HttpCacheability.Public);

I know that's not exactly what you're asking for, but I found this question via Google and figure others might like this answer as it's related to the APIs you show in the original question text.

answered Jun 22 '11 at 16:04

Drew Noakes

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Shouldn't that be DateTime.UtcNow? If not, can you explain how the browser knows what the local time of the server is? (Update: actually http://stackoverflow.com/questions/4849744/should-i-use-datetime-now-or-datetime-utcnow-in-httpcookie-expires-and-httpcache answers this question) – Michiel Cornille May 10 '16 at 15:22
1

Good question. As you discovered, it doesn't matter. – Drew Noakes May 10 '16 at 17:15

score 2 · Answer 3 · answered Apr 09 '10 at 16:28

2

Look at mini static content delivery project. :)

answered Apr 09 '10 at 16:28

dariol

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How to specify HTTP expiration header? (ASP.NET MVC+IIS)

3 Answers3

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