WP 图片加载时显示加载中

private BitmapImage srcimage = new BitmapImage();

        public MainPage()
        {
            InitializeComponent();

            progressBar1.IsIndeterminate = false; //进度条

            srcimage.CreateOptions = BitmapCreateOptions.None; //不延时加载
            
            srcimage.ImageOpened += new EventHandler<RoutedEventArgs>((sender, e) =>
            {
                progressBar1.IsIndeterminate = false;
                image1.Source = srcimage;
            });
        }

        private void wc_picOpenReadImg(string url)
        {
            if (DeviceNetworkInformation.IsNetworkAvailable)
            {
                progressBar1.IsIndeterminate = true;

                //显示加载中的图片
                srcimage.UriSource = new Uri("/Images/xxxxxx.png", UriKind.Relative);

                //网络上的图片
                srcimage.UriSource = new Uri(url, UriKind.Absolute);
            }
            else
            {
                MessageBox.Show("网络未打开，请检查wifi或数据是否已开启。");
            }
        }