Google Map บน Windows Phone 8 ต้องใช้ Toolkit หรือ referrentตัวไหนบ้าง

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
namespace GooglemapTest
{
    public class GoogleTile : Microsoft.Phone.Controls.Maps.TileSource
    {
        private int _server;
        private char _mapmode;
        private GoogleTileTypes _tiletypes;
        public GoogleTileTypes TileTypes
        {
            get { return _tiletypes; }
            set
            {
                _tiletypes = value;
                MapMode = MapModeConverter(value);
            }
        }
        public char MapMode
        {
            get { return _mapmode; }
            set { _mapmode = value; }
        }
        public int Server
        {
            get { return _server; }
            set { _server = value; }
        }
 
        public GoogleTile()
        {
            UriFormat = @"http://mt%7B0%7D.google.com/vt/lyrs=%7B1%7D&z=%7B2%7D&x=%7B3%7D&y=%7B4%7D";
            Server = 0;
        }
 
        public override Uri GetUri(int x, int y, int zoomLevel)
        {
            if (zoomLevel > 0)
            {
                var Url = string.Format(UriFormat, Server, MapMode, zoomLevel, x, y);
                return new Uri(Url);
            }
            return null;
        }
 
        private char MapModeConverter(GoogleTileTypes tiletype)
        {
            switch (tiletype)
            {
                case GoogleTileTypes.Hybrid:
                    {
                        return 'y';
                    }
                case GoogleTileTypes.Physical:
                    {
                        return 't';
                    }
                case GoogleTileTypes.Satellite:
                    {
                        return 's';
                    }
                case GoogleTileTypes.Street:
                    {
                        return 'm';
                    }
                case GoogleTileTypes.WaterOverlay:
                    {
                        return 'r';
                    }
            }
            return ' ';
        }
        public enum GoogleTileTypes
        {
            Hybrid,
            Physical,
            Street,
            Satellite,
            WaterOverlay
        }
    }
}