ASP.NET @OuputCache Directive "Inheritance"

Question

Hi to all,

As I mention in an earlier question, I am having trouble with the performance of a web site... Some SQL queries are killing the server. But, as the title of this post mention, I looked at the OutputCache page directive to improve performance of the site.

Although, I came across some questions regarding this directive: 1- If I have a web-user control that declares an OuputCache directive in a page that has one too, which one will "win" ? 2- What's the best pratice regarding the duration ? I'd love to have a sliding window too.

Thanks for your help and please visit http://www.developerit.com

Answer 1

Hi,
Here's a good article on Output caching: http://www.4guysfromrolla.com/articles/121306-1.aspx.

Generally, you seem to be looking at Page and Fragment caching. What you want to do is cache the Page, if you can, as that will give you the best performance benefit. But, if you have regions on the page that must change dynamically per user, eg: you are saying 'Hi {username}' at the top of the page, then you need to look at Fragment caching.

Fragment caching is not as effective as page caching, since the output has to be stitched together from cached info and dynamic info, but it's usually still MUCH better than NO caching!

It's a bit of an art, to tweak the caching depending on what the page does and the load on the database, but it can make a page load many Orders of Magnitude faster than non-cached.

FYI - if the db queries are killing the site you may want to also look at taming them and/or caching their output individually, so that you don't have to keep hitting the database for the same information.

Also understand the 'varyByParam' for caching is pretty useful too - say you have a page in 3 languages, you can cache a page for each language by using the varyByParam, as long as your Url some sort of language component that the varyByParam can pick up.

HTH, Lance

Answer 2

On a request where neither are cached, both the page and the control will be created, and then added to the output cache. If the page is cached, the control will not be created, regardless of whether it's in the cache or not--its markup is contained in the cached copy of the page. If the page is not cached and the control is, the cached markup of the control will be used in the page.