I had my ASP.NET 2.0 application hosted on Windows 2003 Sever with IIS 6.0. After Visual Studio 2010 or more precisely after .NET Framework 4.0, I upgraded the desktop modules to 4.0 (version 3.0 and 3.5 are superset, not the framework). The transition of desktop application from 2.0 to 4.0 was smooth enough. Although there were some deep level changes required in some scenarios (minor ones) but overall it was simple. The application executed properly in the first attempt.
I updated the Web Modules also but did not deploy them (in production environment only). Recently, it was planned to deploy the upgraded module. I installed the framework 4.0 on the web server and using the existing Publish settings, I published the upgraded application on the server (test server, not making experiments on the production server). On browsing the page, I got a 404 Page not found error. It was really a wired and unexpected situation. I have read about the issue of upgrading from IIS 6.0 to IIS 7.0 specially related to web.config but this transition error was totally not expected.
After a lot of search and attempts, I was able to execute the application. Below are the minimum steps required for it:
- In IIS 6 console, right click you project and click the properties and check the ASP.Net tab whether Framework 4 is selected or not. If not select the framework 4.
- In IIS 6 single application pool can’t be used for two different frameworks. Add a new pool with any meaningful name. Application Pools is above the Default
Website node in the main tree hierarchy. (IIS 7 supports)
- To assign the application pool, in IIS console open the properties section of the web application, and click on the Home Directory tab and select newly created application pool from the drop-down-list.
Basically Page not found issue is cause of other problem which is set hidden by IIS6. But you need to see the real cause.
- For this open IIS6 console and in the main hierarchy, select Web Service Extension node which is right below the Default Website node. You will see the entire ASP.Net framework list over there, by default these frameworks might be set to Prohibited so select ASP.Net Framework 4 and click Allow button.
Browse you website now and it should be working.
If you are having some other errors, check the source link.