As many of you have, I also have experimented with the pre-releases of .NET 3.5 and Visual Studio codenamed Orcas. I, for better or worse, installed this pre-release software on my primary development machine which has Visual Studio 2005.
Despite having .NET 3.5 installed on my machine, my primary development occurred in .NET 2.0 via Visual Studio 2005. I had not experienced any problems with this setup until the other day. While attempting to build and publish an ASP.NET 2.0 website with AJAX extensions, I ran into a cryptic server error when executing the site on a staging server. The error was:
Could not load file or assembly 'System.Web.Extensions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'
or one of its dependencies. The system cannot find the file specified.
The System.Web.Extensions assembly is the ASP.NET AJAX assembly, so at first I simply thought that the staging server did not have AJAX extensions installed. After installing the AJAX extensions, the issue remained unresolved. A quick look in the machine’s GAC showed that it had version 1.0.61025.0, which is the latest version. Inspection of my development machine’s GAC showed both 1.0.61025.0 and 2.0.0.0 installed.
At this point I was puzzled how my machine had an unofficial version of AJAX extensions, and how my website was referencing it. Next I looked at the web.config of my site to see if I could just change the referenced version to 1.0. However, inspection of the web.config reveled:
<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
</add>