MVC3 Upgrade The type 'System.Web.Mvc.AcceptVerbsAttribute' exists in both

If after following the manual upgrade instructions you receive an error such as "The type 'System.Web.Mvc.AcceptVerbsAttribute' exists in both " you should try the following:

 

 

  1. Right click on the web site and view the properties -> and in the references section make sure you do not have duplicate references...if you do, delete one of them
  2. Check you bin directory, if you have System.Web.Mvc.dll in the bin, remove it (you may also need to remove System.Web.Abstractions.dll, etc.


    You should then be able to build 

 

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