My setup: ASP.NET 4.0 Web Site running on IIS 6.0.
I have a site with many landing pages with virtual URLs, all being served by a single physical landingpage.aspx file (via ASP.NET 4.0 Routing), in which I use the OutputCache directive, caching the page on the server for 24 hours.
Recently, I started to experience a problem that the __doPostBack JavaScript block was missing from some of the generated pages. There is a LinkButton in the page (inside a webusercontrol), so the JS block should be there, but sometimes it isn’t. This is naturally leading to JS errors in the browser upon clicking the LinkButton.
My suspicion is that maybe on the first visit to a given URL handled by the above mentioned physical .aspx file it might have been a visit by a client (a browser or a search bot) which maybe was considered by ASP.NET as a down-level browser, and therefore the doPostBack was not output into the generated cached version of the page, and then this wrong cached version is served to all the subsequent visitors…? On the other hand, I’d say ASP.NET is smart enough to generate different cached version for different levels of browsers, isn’t it?
Nevertheless, my question is: can I find the cached files that are served to the visitors somewhere on the server, and somehow check if my assumptions are correct? Also, I would like to disable this ASP.NET recognition of browsers altogether and serve the same content to every browser, just as it would serve to any modern browser.
Thanks a lot for any advice and help.
Answering my own question: Confirmed that the website was sending back HTML without __doPostBack() for unrecognized browsers. Adding ClientTarget=”uplevel” to the @ Page directive at the top of the .aspx page in question solved the problem and __doPostBack() block is now always present.