Windows Server 2008, ASP.NET, Pre-compiling and Virtual Directories

windowsserver2008 There has been an interesting problem at work over the last couple of weeks. We are in the process of preparing to move service providers and at the same time upgrading all our servers to run Windows Server 2008 and SQL Server 2008. In preparation for this move, we have been upgrading our staging and test servers so we can be sure that everything will work as expected and to iron out the processes, so the move goes as smoothly as possible.

It took about ten minutes before we hit the strangest of problems. It was focused around the way we use a virtual directory to share common code and controls across different websites. The premise is that you create a project to hold your common javascript/images/ascx controls/web services and so on. You then use a virtual directory inside each of your websites that points to the common project. With only a small amount of tweaking for the common ascx controls everything seems to work without too much trouble. That is, until you try to do this on Windows Server 2008.

When we started up our web application on our new environment, we noticed almost immediately that the AJAX calls that used the common web service were failing. The error message was suggesting that the project that contained the common web service has not been compiled correctly. By copying the website across to a Windows 2003 server, we deduced that the problem was specific to 2008 as it worked perfectly on 2003. Having exhausted all the developers ideas on why this would be, we called Microsoft and got them involved in troubleshooting the issue.

A few days later an answer came: do not pre-compile your website. Sure enough, build the website without pre-compilation and it worked perfectly. Microsoft’s explanation was that it was due to a change in the way that Windows Server 2008/IIS7 worked. Fairly cryptic I must say and certainly does not leave me satisfied as to why it would not work and what have they done to stop it working. For us, using Windows Server 2008 and IIS7 is more important than the slight performance hit you get when deploying without pre-compilation. For others it may not be such a desirable solution.


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