DataContractJsonSerializer not available
Well thanx to Yaakov I figured out what happened. For those using DataContractJsonSerializer for the first time remember to manually add the reference to System.Runtime.Serialization once you do that you should be able to resolve "using System.Runtime.Serialization.Json;"
In my case i guess when after adding the reference i just saw that VS wasn't happy and then did not manually build it. So i was on the right track just didn't give it enough time :)