System.Json does not exist in VS 2012 with .net 4.5.2

Hi

I don't seem to be able to include the System.Json namespace with VisualStudio 2012 update 4 and the .net Framework 4.5.2.

What I tried:
- install update 4 for VisualStudio
- install the new .net Framework 4.5.2
- searching for System.Json in Add Reference
- install System.Json (Beta) over NuGet (failed (already has a reference to 'System.Json 4.0.20126.16343'))
- setting the TargetFramework for every subproject to 4.5.2

Do you have any idea?

UPDATE:

I've searched with the Object Browser through the .net Framework 4.5.2 but was unsuccessful, looks like it does not even exist yet.

http://msdn.microsoft.com/en-us/library/system.json(v=vs.110).aspx

As marked on this page it is only a preview, despite being available for .net 4.5

So I will have to use System.Runtime.Serialization.Json instead.