VS2010命名空间Microsoft中不存在类型或命名空间名称Web，是否缺少程序集引用?

using System;
using Microsoft.Web.Administration;

namespace ConsoleApplication1
{
    class Program
    {       
        public static void Main(string[] args)
        {
            ServerManager iis = new ServerManager();
            SiteCollection sites = iis.Sites;
            foreach (Site site in sites)
            {
                Console.WriteLine(site.Name);
            }

            Console.ReadKey();
        }
    }
}