Cannot get decorator attributes recognized by Intellisense (newbie question)

I got web services to work, even returning complex classes for a client, even remotely, etc, but strangely i cannot get any attributes to be recognized save one:  [WebMethod] (and a few others added automatically by Visual Studio).
My book has an example for [DataContract] as well as[Datamember], but they fail to be recognized by Intellisense.
Any ideas?
see code below, both the code-behind as well as the web.config file. Environment is ASP.NET using C# for Visual Studio 2008 Express.
MS
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Threading;
using System.Runtime.Serialization;
 
namespace DuplexContractWebServ
{
    /// <summary>
    /// Summary description for DuplexService1
    /// </summary>
& ...