为什么使用WebClient不能上载~是模拟器出有关问题吗

为什么使用WebClient不能下载~~是模拟器出问题吗？
貌似不能下载那张图片~~总是不显示~~~要点击那个显示图片流的键~
下载的进度条也不会走~~

MainPage.xaml.cs文件：

C# code

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 Microsoft.Phone.Controls;using System.Windows.Media.Imaging;using System.Text;using System.IO;namespace ImageToByte{    public partial class MainPage : PhoneApplicationPage    {        // 构造函数        public MainPage()        {            InitializeComponent();        }        private void button1_Click(object sender, RoutedEventArgs e)        {            try            {                Uri img = new Uri("http://img6.ph.126.net/xMMHX5vxqilnYgG7qxSkYQ==/6597751463865557506.jpg", UriKind.RelativeOrAbsolute);                //使用WebClent下载图片                WebClient wc = new WebClient();                //注册OpenRead事件                wc.OpenReadCompleted += new OpenReadCompletedEventHandler(wc_OpenReadCompleted);                //下载进度事件                wc.DownloadProgressChanged +=new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);                //异步调用                wc.OpenWriteAsync(img);            }            catch (Exception es)            {                MessageBox.Show(es.Message);            }        }        void wc_OpenReadCompleted(object sender,OpenReadCompletedEventArgs e)         {            Stream stream = e.Result;            BitmapImage bitmap = new BitmapImage();            bitmap.SetSource(stream);            showImage.Source = bitmap;                    }        void wc_DownloadProgressChanged (object sender,DownloadProgressChangedEventArgs e)        {            this.Dispatcher.BeginInvoke(() =>            {                progressBar1.Value = e.ProgressPercentage;            });        }    }}

XML code

<phone:PhoneApplicationPage     x:Class="ImageToByte.MainPage"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"    mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768"    FontFamily="{StaticResource PhoneFontFamilyNormal}"    FontSize="{StaticResource PhoneFontSizeNormal}"    Foreground="{StaticResource PhoneForegroundBrush}"    SupportedOrientations="Portrait" Orientation="Portrait"    shell:SystemTray.IsVisible="True">    <!--LayoutRoot 是包含所有页面内容的根网格-->    <Grid x:Name="LayoutRoot" Background="Transparent">        <Grid.RowDefinitions>            <RowDefinition Height="Auto"/>            <RowDefinition Height="*"/>        </Grid.RowDefinitions>        <!--TitlePanel 包含应用程序的名称和页标题-->        <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">            <TextBlock x:Name="ApplicationTitle" Text="我的应用程序" Style="{StaticResource PhoneTextNormalStyle}"/>            <TextBlock x:Name="PageTitle" Text="页面名称" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>        </StackPanel>        <!--ContentPanel - 在此处放置其他内容-->        <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">            <Button Content="显示图片流" Height="72" HorizontalAlignment="Left" Margin="27,272,0,0" Name="button1" VerticalAlignment="Top" Width="183" Click="button1_Click" />            <Button Content="显示图片" Height="72" HorizontalAlignment="Right" Margin="0,272,38,0" Name="button2" VerticalAlignment="Top" Width="160" />            <Image Height="260" HorizontalAlignment="Left" Margin="6,6,0,0" Name="showImage" Stretch="Fill" VerticalAlignment="Top" Width="444" />            <ScrollViewer Height="201" HorizontalAlignment="Left" Margin="9,400,0,0" Name="scrollViewer1" VerticalAlignment="Top" Width="441">                <TextBlock Height="30" Name="showCode" Text="TextBlock" />            </ScrollViewer>            <ProgressBar Height="26" HorizontalAlignment="Left" Margin="6,350,0,0" Name="progressBar1" VerticalAlignment="Top" Width="460" />        </Grid>    </Grid>     <!--演示 ApplicationBar 用法的示例代码-->    <!--<phone:PhoneApplicationPage.ApplicationBar>        <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">            <shell:ApplicationBarIconButton IconUri="/Images/appbar_button1.png" Text="按钮 1"/>            <shell:ApplicationBarIconButton IconUri="/Images/appbar_button2.png" Text="按钮 2"/>            <shell:ApplicationBar.MenuItems>                <shell:ApplicationBarMenuItem Text="菜单项 1"/>                <shell:ApplicationBarMenuItem Text="菜单项 2"/>            </shell:ApplicationBar.MenuItems>        </shell:ApplicationBar>    </phone:PhoneApplicationPage.ApplicationBar>--></phone:PhoneApplicationPage>