Silverlight 中的WebClient 与 WebRequest 示例

WebClient

public partial class webclientSample : UserControl
  {
      public webclientSample()
      {
          InitializeComponent();
          //定义URL地址
          string url = "http://localhost:2365/Sample.web/responseText.htm";
          //创建WebClient对象
          WebClient webClient = new WebClient();
          //定义异步请求地址
          webClient.DownloadStringAsync(new Uri(url
              , UriKind.RelativeOrAbsolute));
          //定义请求完成的事件处理
          webClient.DownloadStringCompleted +=
              new DownloadStringCompletedEventHandler
                  (webClient_DownloadStringCompleted);
      }

      private void webClient_DownloadStringCompleted(object sender
          , DownloadStringCompletedEventArgs e)
      {
          //显示返回值
          MessageBox.Show(e.Result.ToString());
      }
  }

WebRequest

public partial class webrequestSample : UserControl
    {
        //定义异步委托方法
        private delegate void DispatcherInvoke(string str);
        public webrequestSample()
        {
            InitializeComponent();
            //定义URL地址
            string url = "http://localhost:1398/Sample.web/responseText.htm";
            //创建WebClient对象
            WebRequest request =
                HttpWebRequest.Create(new Uri(url
                    , UriKind.RelativeOrAbsolute));
            //开始获取响应并进行异步回调
            request.BeginGetResponse(new AsyncCallback(responseReady)
                , request);
        }
        private void responseReady(IAsyncResult ar)
        {
            //返回异步回调结果对象
            WebRequest request = ar.AsyncState as WebRequest;
            //获取结果响应对象
            WebResponse response = request.EndGetResponse(ar);
            //定义返回流对象
            using (Stream stream = response.GetResponseStream())
            {
                //使用流读取对象
                StreamReader reader = new StreamReader(stream);

                //*** 直接读取将发生错误。
                //tbk.Text = "reader.ReadToEnd();

                //使用Dispatcher异步执行委托方法
                tb.Dispatcher.BeginInvoke
                    ((DispatcherInvoke)processResult
                    , reader.ReadToEnd());
            }
        }
        private void processResult(string result)
        {
            //显示返回字符串
            tb.Text = result;
        }
    }