WebResource.axd Caching Explained and How It Works

We’ve moved our site from .NET 1.1 to .NET 3.5, and in the process upped several revs of the UltraWebGrid (currently running 2008 vol2). We are now getting complaints about site performance.

I looked at Fiddler, and I see that the 6 javascript files being loaded by the grid are loaded from WebResource.axd, and are coming back with a number headers that indicate the content should not be cached:

pragma: no-cache
Cache-Control: no-cache, no-store
Expires: -1

I have seen references to similar behavior in a few places on google, but only when the site is running in debug mode. I have ensured that I’m running a release build and turned off debugging in web.config, but to no avail.

I don’t know that this is an Infragistics problem, but I thought some of you might have run into it before.

Is there a way to configure the headers that asp.net applies to these resources?

Hello,

Indeed, this is a tricky one. By default, ASP.NET generates no-cache pragmas and timestamps for WebResource.axd resources while the application is in debug mode. The reason for that is that this is the only way you can debug script, styles, etc — if they are cached, you will not be able to see the changes and cannot debug.

One you have the application in release mode, ASP.NET will take care of converting the link and pragmas for WebResource.axd so that they are cached.

I highly recommend the following blog post by Rick Strahl on this, very informative:

http://www.west-wind.com/Weblog/posts/4310.aspx

Hope this helps.

After upgrading, uncached WebResource files can hurt performance. Configuring caching headers or bundling scripts may help. Like Cookie Clicker City, small optimizations compound over time into noticeably smoother results.