Running the ASP.NET Windows Live Web site in IIS7, Could not load file or assembly 'System.Web.Extensions, Version=,” Error


When I was trying to run the Windows Live Enabled Website that is shipped with the Windows Live Tools for Visual Studio November 2008 CTP (I had blogged about this earlier at and you can download the CTP from ) against IIS 7, I got the error “Could not load file or assembly ‘System.Web.Extensions, Version=….” error. 

Interestingly this error wasn’t showing up if I create the website in the File Folder that doesn’t use the IIS 7 hosting service.  I had earlier chosen “File – New Website – ASP.NET Windows Live Website” and selected the location as “HTTP” and created the site.  When I was trying to debug, I ran into this issue.  Similarly, when I created a regular ASP.NET Website and tried to add the Windows Live Controls from the ToolBox, I didn’t face this issue.

Apparently, the versioning of the DLLs under the system.webserver setting in the web.config file that was created using my initial approach was referring to the version of the System.Web.Extensions DLL.  This was the preview version that used to be shipped in the earlier days of the ASP.NET 3.5 Extensions Preview.

However, the newer previous that are part of are back referencing the version.

And this issue must have been coming specifically when running against IIS since the version of ASP.NET mapped to my IIS7 script mappings doesn’t have this version of the DLL and also because of the fact that it was looking into the <system.webserver> setting of the web.config file and trying to locate this version. (the system.webserver is interpreted only when running your site against IIS 7, when you run this using the built-in webserver, this section seems to be ignored)

The solution was simple, I renamed the 3.6 versions back to 3.5 and the site started working.  Guess the website template shipped by the Windows Live Team is referring to the old pattern of the extensions preview reference.

Would update this post, if I find a more appropriate solution/fix or corrections.

Cheers !!!

Print | posted on Friday, January 16, 2009 8:05 PM

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# re: Running the ASP.NET Windows Live Web site in IIS7, Could not load file or assembly 'System.Web.Extensions, Version=,”

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running smoothly
Left by online baer on Jan 09, 2010 6:53 AM

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