Output Caching on the Server AND Client

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nkranes@gmail.com - 12 Nov 2004 17:09 GMT

I have ASP.NET pages that I want cached on BOTH the client and server
sides. I am currently setting the cache policy through code rather
than OutputCache directive:

HttpContext.Current.Response.Cache.SetValidUntilExpires(true);
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.Public);
HttpContext.Current.Response.Cache.SetExpires(DateTime.Now.AddMinutes(10);

This seems to work fine as the pages are being cached on the client.
My question is does the page actually get cached on the client AND
server side. I.e. After a page is expired on the client and a request
is made to the server, is a server-side cached version of the page
returned? Or is the page re-executed on the server for every single
client whose copy has expired?

Thanks in advance!

Neal

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Ben Strackany - 12 Nov 2004 21:39 GMT

The page will not be cached server-side unless you use the outputcache
feature. The code you listed is only caching client-side.

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Ben Strackany
www.developmentnow.com

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> I have ASP.NET pages that I want cached on BOTH the client and server
> sides. I am currently setting the cache policy through code rather
> than OutputCache directive:
>
> HttpContext.Current.Response.Cache.SetValidUntilExpires(true);

HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.Public);

> HttpContext.Current.Response.Cache.SetExpires(DateTime.Now.AddMinutes(10);
>
[quoted text clipped - 8 lines]
>
> Neal

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Ben Strackany - 19 Nov 2004 23:22 GMT

My bad, I was reading it wrong. I should have said that your code is caching
client side & server side.

Response.Cache.SetExpires & Response.Cache.SetCacheability

are interchangeable with the @outputcache parameter

which AFAIK will invoke server-side & client-side caching per the location
parameter.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/c
pconOutputCache.asp

Signature

Ben Strackany
www.developmentnow.com

<a href="http://www.developmentnow.com">dn</a>

> The page will not be cached server-side unless you use the outputcache
> feature. The code you listed is only caching client-side.
[quoted text clipped - 4 lines]
> >
> > HttpContext.Current.Response.Cache.SetValidUntilExpires(true);

HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.Public);

HttpContext.Current.Response.Cache.SetExpires(DateTime.Now.AddMinutes(10);

> > This seems to work fine as the pages are being cached on the client.
> > My question is does the page actually get cached on the client AND
[quoted text clipped - 6 lines]
> >
> > Neal

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Joerg Jooss - 12 Nov 2004 21:58 GMT

> I have ASP.NET pages that I want cached on BOTH the client and server
> sides. I am currently setting the cache policy through code rather
[quoted text clipped - 10 lines]
> returned? Or is the page re-executed on the server for every single
> client whose copy has expired?

In additon to Ben's reply, let me add you're confusing HTTP caching with
application server specific caching. Your code makes your content cacheable
on web clients and proxies, but has nothing to do with ASP.NET owns caching
facilities.

BTW, you should also call

TimeSpan ts = new TimeSpan(0, 10, 0);
HttpContext.Current.Response.Cache.SetMaxAge(ts);

for full HTTP 1.1 compliance.

Cheers,

Signature

Joerg Jooss
www.joergjooss.de
news@joergjooss.de

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nkranes@gmail.com - 12 Nov 2004 22:28 GMT

So what you're saying is that to enable Client-side (HTTP) and Server
side (Application) caching I need to include the above code plus the
outputcache directive? According to the documentation, I thought
Response.Cache and the OutputCache were used interchangably?

>From help:

You can enable or disable page output caching for cache-capable devices
in the request stream either declaratively or programmatically as well.
In the @ OutputCache directive for a page you can use the Location
attribute to specify whether the page's output can be cached on proxy
servers, browser clients, the originating Web server, or all or none of
these. You can do the same programmatically using the
HttpCachePolicy.SetCacheability method to specify the appropriate
HttpCacheability enumeration value for your page.

Thoughts?

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Joerg Jooss - 13 Nov 2004 11:09 GMT

> So what you're saying is that to enable Client-side (HTTP) and Server
> side (Application) caching I need to include the above code plus the
> outputcache directive?

No...

> According to the documentation, I thought
> Response.Cache and the OutputCache were used interchangably?

Yes, you can. Actually, I should have written "HttpCachePolicy mixes up HTTP
caching and application server specific caching".

There's no notion of caching content on the origin server in HTTP, thus
setting HTTP headers using @OutputCache or HttpCachePolicy only affects
downstream proxies or clients.

If you want to have your cake and eat it, use
<%@ OutputCache Duration="600" VaryByParam="None" Location="Any" %>

This will allow caching everywhere. Even if a client request gets back to
the origin ASP.NET server, it simply replies with the cached response but
counts down the "Cache-Control: max-age" header -- very nice!

Cheers,

Signature

Joerg Jooss
www.joergjooss.de
news@joergjooss.de

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nkranes@gmail.com - 15 Nov 2004 20:24 GMT

I hate to say it but you are correct. The only way to cache on the
Server and Client seems to be using the OutputCache directive. I still
think the documentation for the caching API is a bit misleading in this
regard and that there should be a way to programmatically do this.
Thanks for your help!

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Ben Strackany - 19 Nov 2004 23:56 GMT

The documentation seems to imply that they're interchangeable, but maybe
not.

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Ben Strackany
www.developmentnow.com

<a href="http://www.developmentnow.com">dn</a>

> I hate to say it but you are correct. The only way to cache on the
> Server and Client seems to be using the OutputCache directive. I still
> think the documentation for the caching API is a bit misleading in this
> regard and that there should be a way to programmatically do this.
> Thanks for your help!

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Joerg Jooss - 21 Nov 2004 08:22 GMT

> I hate to say it but you are correct. The only way to cache on the
> Server and Client seems to be using the OutputCache directive. I
> still think the documentation for the caching API is a bit misleading
> in this regard and that there should be a way to programmatically do
> this. Thanks for your help!

Actually, I didn't want to imply that the "Any" option is only available
through OutputCache directive. It was only your reply that made me check
again. And yes, there seems to be no direct equivalent of Location="Any"
when using the API, but I'm sure you can construct it using several
HttpCachePolicy calls.

Cheers,

Signature

Joerg Jooss
www.joergjooss.de
news@joergjooss.de

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Output Caching on the Server AND Client

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