Как исправить отсуствие WebClient?

Делаю скачивание файла на Windows Mobile в Visual Studio 2008 C# вот код:

using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using System.Net;

namespace LimonMarket
{
    public class FA
    {
        public void download(string fromfile, string to) {
            WebClient webClient = new WebClient();
            webClient.DownloadFile(fromfile, to);

        }
    }
}

Пишет ошибку : Error 2 The type or namespace name 'WebClient' could not be found (are you missing a using directive or an assembly reference?) C:\Users\stepa\Documents\Visual Studio 2008\Projects\LimonMarket\LimonMarket\FA.cs 12 13 LimonMarket Error 3 The type or namespace name 'WebClient' could not be found (are you missing a using directive or an assembly reference?) C:\Users\stepa\Documents\Visual Studio 2008\Projects\LimonMarket\LimonMarket\FA.cs 12 39 LimonMarket