如何在异步加载的数据处理中使用Linq

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;
using System.Collections.Generic;
using System.ComponentModel;
using ClientPortal.RIA.Web;
using System.ServiceModel.DomainServices.Client;
using ClientPortal.Server.Model;
using ClientPortal.Mvvm;
using System.Linq; //必须引用命名空间；
using System.Windows.Media.Imaging;
using System.IO;
using System.Windows.Threading;


要引用命名空间才能在WCF RIA的Entities使用linq的查询或操作：
if (lo.Entities != null && lo.Entities.Count<ThumbnailImageInfo>() == 1)                {                    ThumbnailImageInfo img = lo.Entities.First<ThumbnailImageInfo>();