C# in PowerShell: Errors with "using System.Linq'

Hi , I'm trying to execute C# code in Power Shell 2.0 .

My problem is for the references  at the beginning of the code:


$code = @"

using System;
using System.Collections;
using System.IO;
using System.Linq;
using System.Xml;<code></code>
using System.Xml.Linq;

   public class Program
    {
        static void Main()
        {  /* the code wich works*/


        }


    }


"@
Add-Type  -TypeDefinition $code -Language "CSharpVersion3"

Powershell gives me an error saying that " The type or namespace Linq doesn't exist" , and the same for Xml. I have Visual studio express 2013 .

How can add or import correctly those references? or what is my error?