Windows Store errors

 using System.Net;
 using System.IO;
 public static bool HasConnection()
     {
         try
         {
             IPHostEntry i = Dns.GetHostEntry("www.google.com");
             return true;
         }
         catch
         {
             return false;
         }
     }

It compiles with Android, but crashes with WindowsPhone store, can't figure out why, any help? I have such errors with WP.

 Assets\HSController.cs(111,4): error CS0246: The type or namespace name 'IPHostEntry' could not be found (are you missing a using directive or an assembly reference?)
 Assets\HSController.cs(111,20): error CS0103: The name 'Dns' does not exist in the current context