异步请求类HttpClient

using System;
using System.Net;
using System.Windows;
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);
            }
        }
    }
}