关于WCF RIA Service 删除操作的有关问题？先多谢了

关于WCF RIA Service 删除操作的问题？请教各位，先谢谢了
silverlight4 + sql2008 +.net2010
1、添加了Movie的ADO.NET数据实体类型
2、添加了Movie的DomainService类
3、拖拽了MovieDomainContext到主页
4、想进行删除操作，以下是代码，删除后在this.movieCtx.Movies.Remove(movie)处抛出错误：
the specified entity is not contained in this entityset.
请教什么地方写错了？

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.ServiceModel.DomainServices.Client;
using SLA20131012.Web;

namespace SLA20131012
{
    public partial class MainPage : UserControl
    {
        private MovieDomainContext movieCtx = new MovieDomainContext();
        
        public MainPage()
        {
            InitializeComponent();
            bt_del.Click += new RoutedEventHandler(bt_del_Click);         
        }     

        private void bt_del_Click(object sender, RoutedEventArgs e)
        {
            Movie movie = movieDataGrid.SelectedItem as Movie;
            this.movieCtx.Movies.Remove(movie);  //此处抛出错误
            this.movieCtx.SubmitChanges();

        }

        private void movieDomainDataSource_LoadedData(object sender, System.Windows.Controls.LoadedDataEventArgs e)
        {

            if (e.HasError)
            {
                System.Windows.MessageBox.Show(e.Error.ToString(), "Load Error", System.Windows.MessageBoxButton.OK);
                e.MarkErrorAsHandled();
            }
        }


    }
}





------解决方案--------------------

引用:

http://pan.baidu.com/s/1vHOJY

上传到百度网盘了，有数据库文件 先谢谢了

我是改成这样成功的：

    <Grid x:Name="LayoutRoot" Background="White">

        <Button Content="删除" Height="23" HorizontalAlignment="Left" Margin="12,208,0,0" Name="bt_del" VerticalAlignment="Top" Width="75" Click="bt_del_Click" />        

        <sdk:DataGrid AutoGenerateColumns="True" Height="190" HorizontalAlignment="Left" ItemsSource="{Binding ElementName=movieDomainDataSource, Path=Data}" Margin="12,12,0,0" Name="movieDataGrid" RowDetailsVisibilityMode="VisibleWhenSelected" VerticalAlignment="Top" Width="164"/>

    </Grid>

namespace SLA20131012

{

    public partial class MainPage : UserControl

    {

        private MovieDomainContext movieCtx = new MovieDomainContext();

        

        public MainPage()

        {

            InitializeComponent();


            LoadOperation<Movie> loadMovies = movieCtx.Load(movieCtx.GetMovieQuery());

            loadMovies.Completed += loadMovies_Completed;