Unable to compile an ASP.NET 2.0 project in Visual Studio 2010 on Windows 7 x64/x32 that references System.Web.Extensions (ASP.NET AJAX 1.0).

If your project is referencing some dll which has a dependency on System.Web.Extensions.dll then it is most lilkely that you may receive this error –

The primary reference “MyClass, Version=, Culture=neutral, processorArchitecture=MSIL” could not be resolved because it has an indirect dependency on the framework assembly “System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35” which could not be resolved in the currently targeted framework. “.NETFramework,Version=v2.0”. To resolve this problem, either remove the reference “MyClass, Version=, Culture=neutral, processorArchitecture=MSIL” or retarget your application to a framework version which contains “System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35”.

Solution –

1) Download and install Asp.Net AJAX 1.0

2) Add a particular entry in the registry.

Step 1

    Download Asp.Net AJAX 1.0 from http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=883 and install it.

Step 2

   If your operating system is 64 bit then add this entry in the system registry.

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v2.0.50727\AssemblyFoldersEx\ASP.NET AJAX Extensions] – =”C:\Program Files (x86)\Microsoft ASP.NET\ASP.NET 2.0 AJAX Extensions\v1.0.61025\”

For 32 bit systems, add this

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v2.0.50727\AssemblyFoldersEx\ASP.NET AJAX Extensions] – =”C:\Program Files\Microsoft ASP.NET\ASP.NET 2.0 AJAX Extensions\v1.0.61025″



  1. Johnatan says:

    I was having a hard time compiling an old project (which I can’t upgrade to a newer version of the framework). After hours of guesswork and bad leads, this old post saved me.

    Can’t believe installing the Ajax Extensions wouldn’t register this key by itself.

  2. Viviane says:

    Thank you!! It worked, I spent almost a day trying to resolve this problem.


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