silverlight向服务器post数据类

using System;
 using System.Net;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Documents;
 using System.Windows.Ink;
 using System.Windows.Input;
 using System.Windows.Media;
 using System.Windows.Media.Animation;
 using System.Windows.Shapes;
 using System.IO;
 
 
 public class HttpClient
 {
 private WebRequest webRequest = null;
 public delegate void ResponseEventHandler(String responseResult);
 public event ResponseEventHandler onResponseEventHandler;
 public delegate void RequestEventHandler();
 public event RequestEventHandler onRequestEventHandler;
 public string PostData { get; set; }
 
 public HttpClient(Uri clientUri)
     {
         Uri endpoint = clientUri;
         webRequest = WebRequest.Create(endpoint);
         webRequest.ContentType = "application/x-www-form-urlencoded";
         webRequest.Method = "POST";
     }
 
 public void Post()
     {
         webRequest.BeginGetRequestStream(new AsyncCallback(RequestReady), webRequest);
     }
 private void RequestReady(IAsyncResult asyncResult)
     {
 if (this.onRequestEventHandler != null)
         {
 this.onRequestEventHandler();
         }
         WebRequest request = asyncResult.AsyncState as WebRequest;
         Stream requestStream = request.EndGetRequestStream(asyncResult);
 
 using (StreamWriter writer = new StreamWriter(requestStream))
         {
             writer.Write(this.PostData);
             writer.Flush();
             writer.Close();
         }
         webRequest.BeginGetResponse(new AsyncCallback(ResponseReady), webRequest);
     }
 private void ResponseReady(IAsyncResult asyncResult)
     {
 if (this.onResponseEventHandler != null)
         {
             WebRequest request = asyncResult.AsyncState as WebRequest;
             WebResponse response = request.EndGetResponse(asyncResult);
 
 using (Stream responseStream = response.GetResponseStream())
             {
                 String responseResult = String.Empty;
 try
                 {
                     StreamReader reader = new StreamReader(responseStream);
                     responseResult = reader.ReadToEnd();
                 }
 catch (WebException er)
                 {
                     responseResult = er.Message;
                 }
 catch (Exception er)
                 {
                     responseResult = er.Message;
                 }
 this.onResponseEventHandler(responseResult);
             }
         }
     }
 }