求Silverlight4调用摄像头的代码,该如何处理

求Silverlight4调用摄像头的代码
不要求多少功能，只要能捕捉摄像头数据就ok
[解决办法]

# CaptureSource source = new CaptureSource();  
#   
#         private void UserControl_Loaded(object sender, RoutedEventArgs e)  
#         {  
#             VideoCaptureDevice vcd;  
#             //话筒就换成这个类 AudioCaptureDevice  
#             vcd = CaptureDeviceConfiguration.GetDefaultVideoCaptureDevice();  
#   
#             source.VideoCaptureDevice = vcd;  
#   
#             VideoBrush video = new VideoBrush();  
#             video.SetSource(source);  
#             rectangle1.Fill = video;  
#   
#             //截图的回调  
#             source.CaptureImageCompleted += new EventHandler<CaptureImageCompletedEventArgs>(source_CaptureImageCompleted);  
#               
#         }  
#   
#         //截图调用 source.CaptureImageAsync();  
#         void source_CaptureImageCompleted(object sender, CaptureImageCompletedEventArgs e)  
#         {  
#             WriteableBitmap img = e.Result;  
#         }  
#   //此处开始启动
#         private void button1_Click(object sender, RoutedEventArgs e)  
#         {  
#             if (CaptureDeviceConfiguration.AllowedDeviceAccess 
[解决办法]
  
#     CaptureDeviceConfiguration.RequestDeviceAccess())  
#             {  
#                 //启动摄像头 /麦克风以及其他操作  
#                 source.Start();  
#             }  
#         }   

 
 
public partial class Camera : Page
    {
        public Camera()
        {
            InitializeComponent();
            InitLoad();
        }
        private ReadOnlyCollection<VideoCaptureDevice> videoDeviceList;//系统视频列表
        //驱动接管类
        CaptureSource cap = null;
        private void InitLoad()
        {
            //找到系统默认视频
            videoDeviceList = CaptureDeviceConfiguration.GetAvailableVideoCaptureDevices();
            //把找到的视频硬件给Combox显示
            Device.ItemsSource = videoDeviceList.Select(o => o.FriendlyName);
            Device.SelectedIndex = 0;
            if (Device.Items.Count == 1) Device.IsEnabled = false;

            CamaraBtnStar.Click += new RoutedEventHandler(CamaraBtnStar_Click);
            CamaraBtnStop.Click += new RoutedEventHandler(CamaraBtnStop_Click);
            CamaraBtnScreenshots.Click += new RoutedEventHandler(CamaraBtnScreenshots_Click);
        }
        void CamaraBtnStar_Click(object sender, RoutedEventArgs e)
        {
            //视频开始接收
            cap = new CaptureSource();
            //托管驱动得到当前选中的视频设备
            VideoCaptureDevice thisVideo = null;
            if (!string.IsNullOrEmpty(Device.SelectedValue.ToString()))
            {
                thisVideo = videoDeviceList[Device.SelectedIndex];
            }
            if (thisVideo != null)
            {
                cap.VideoCaptureDevice = thisVideo;
                VideoBrush br = new VideoBrush();
                //设置源
                br.SetSource(cap);
                //填充VideoBrush 视频源 
 
                webBrush.Fill = br;
                if (CaptureDeviceConfiguration.RequestDeviceAccess()){
                    cap.Start();
                    if (cap.State == CaptureState.Started)
                    {
                        //视频状态正常就可以截屏了,当异步图像捕获请求返回时发生
                        cap.CaptureImageCompleted += new EventHandler<CaptureImageCompletedEventArgs>(cap_CaptureImageCompleted);
                    }
                }
            }
            else { MessageBox.Show("您的视频出现了异常"); }
        }
        void CamaraBtnStop_Click(object sender, RoutedEventArgs e)
        {
            //如果托管cap不为空
            if (cap.State == CaptureState.Started && cap != null){cap.Stop();}
            else{MessageBox.Show("您没有打开的视频");}

        }
        void CamaraBtnScreenshots_Click(object sender, RoutedEventArgs e)
        {
            //点击截图按钮启动异步图像捕获请求
            if (cap.State == CaptureState.Started && cap != null) {
                cap.CaptureImageAsync();
            }
        }
        void cap_CaptureImageCompleted(object sender, CaptureImageCompletedEventArgs e)
        {
            //具体图像截取事件处理
            var bitmap = e.Result;
            imgCapture.Source = bitmap;
        }





        // 当用户导航到此页面时执行。
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
        }

    }