Silverlight中WebClient下载资源

首先新建一个Silverlight应用程序带Web的，在Web程序中放入一个txt文件，名为TextFile1.txt。内容Silverlight is very good!

然后在silverlight项目中添加一个silverlight user control名为WebClientDownResource.xaml

xaml的内容为：

< Grid  x:Name ="LayoutRoot"  Background ="White" >
         < Grid.ColumnDefinitions >
             < ColumnDefinition >
             </ ColumnDefinition >
         </ Grid.ColumnDefinitions >
         < Grid.RowDefinitions >
             < RowDefinition  Height ="Auto" >
             </ RowDefinition >
             < RowDefinition  Height ="auto" >
             </ RowDefinition >
             < RowDefinition  Height ="auto"   >
             </ RowDefinition >
         </ Grid.RowDefinitions >
        
         < Button  Grid.Row ="1"  Grid.Column ="0"  Content ="DownText"  Height ="23"  HorizontalAlignment ="Left"   Name ="Down"  VerticalAlignment ="Top"  Width ="75"  Margin ="12,0,0,0"  Click ="Down_Click"   />
         < TextBlock   Grid.Row ="0"  Grid.Column ="0"  Height ="23"  HorizontalAlignment ="Left"  Margin ="10,10,0,0"  Name ="textBlock1"  Text ="TextBlock"  VerticalAlignment ="Top"  Width ="350"   />
         < ProgressBar  Grid.Row ="2"  Grid.Column ="0"  Height ="10"  HorizontalAlignment ="Left"  Margin ="10,10,0,0"  Name ="progressBar1"  VerticalAlignment ="Top"  Width ="100"   />

    </Grid> 

后台的代码：

private void Down_Click(object sender, RoutedEventArgs e)

        {
             string  uri  =  Application.Current.Host.Source.AbsoluteUri;
             int  index  =  uri.IndexOf( " /ClientBin " );
            uri  =  uri.Substring( 0 , index)  +   " /TextFile1.txt " ;

            WebClient webClient  =   new  WebClient();
            webClient.OpenReadCompleted  +=   new  OpenReadCompletedEventHandler(webClient_OpenReadCompleted);
            webClient.DownloadProgressChanged  +=   new  DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
            webClient.OpenReadAsync( new  Uri(uri));
        }

         void  webClient_DownloadProgressChanged( object  sender, DownloadProgressChangedEventArgs e)
        {
             this .progressBar1.Value  =  e.ProgressPercentage;
        }
         private   void  webClient_OpenReadCompleted( object  sender, OpenReadCompletedEventArgs e)
        {
             if  (e.Error  !=   null )
            {
                 //  (Add code to display error or degrade gracefully.)
            }
             else
            {
                Stream stream  =  e.Result;
               StreamReader reader = new  StreamReader(stream);
                 this .textBlock1.Text = reader.ReadToEnd();
                reader.Close();
            }
        } 

具体的关于webclient的内容可以参考《pro silverlight 4 in c#》中的第6章内容。