First, It is not just duplicate. None of answers from following questions are working for me.
http://goo.gl/tS40cn
http://goo.gl/pH6v2T
I\'ve just updated al
After trying much of the above (and some other posts), I uninstalled with the package manager all of the following from the project affected:
Microsoft.AspNet.WebApi
Microsoft.AspNet.Client
Microsoft.AspNet.Core
Microsoft.AspNet.WebHost
Newtonsoft.Json
Then reinstalled Microsoft.AspNet.WebApi, which auto installed .Client, .Core, .WebHost, .Json.