title: VS2010 reference dll is missing from the list
body: <p>I'm trying to add System.Web.Extensions.dll to my C# console application so I can parse JSON.
  I'm using VS2010.</p>
  
  <p>When I right click -> Add reference though it does not list the dll.
  However when I search for the file on my computer it does exist.</p>
  
  <p>Please advise on the proper way to add this dll. </p>