using System;using System.Collections.Generic;using System.Configuration;using System.IO;using System.Linq;using System.Net;using System.Text;using System.Threading.Tasks;namespace WebClientAsynProject{  public class Program  {    #region HttpWebRequest異步GET    public static void AsyncGetWithWebRequest(string url)    {      var request = (HttpWebRequest) WebRequest.Create(new Uri(url));      request.BeginGetResponse(new AsyncCallback(ReadCallback), request);    }    private static void ReadCallback(IAsyncResult asynchronousResult)    {      var request = (HttpWebRequest) asynchronousResult.AsyncState;      var response = (HttpWebResponse) request.EndGetResponse(asynchronousResult);      using (var streamReader = new StreamReader(response.GetResponseStream()))      {        var resultString = streamReader.ReadToEnd();        Console.WriteLine(resultString);      }    }    #endregion    #region WebClient異步GET    public static void AsyncGetWithWebClient(string url)    {      var webClient = new WebClient();      webClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);      webClient.DownloadStringAsync(new Uri(url));    }    private static void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)    {      //Console.WriteLine(e.Cancelled);      Console.WriteLine(e.Error != null ? "WebClient異步GET發生錯誤！" : e.Result);    }    #endregion    #region WebClient的OpenReadAsync測試    public static void TestGetWebResponseAsync(string url)    {      var webClient = new WebClient();      webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted);      webClient.OpenReadAsync(new Uri(url));    }    private static void webClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)    {      if(e.Error == null)      {        var streamReader = new StreamReader(e.Result);        var result = streamReader.ReadToEnd();        Console.WriteLine(result);      }      else      {        Console.WriteLine("執行WebClient的OpenReadAsync出錯：" + e.Error);      }    }    #endregion    public static void Main(string[] args)    {      AsyncGetWithWebRequest("http://baidu.com");      Console.WriteLine("hello");      AsyncGetWithWebClient("http://baidu.com");      Console.WriteLine("world");      TestGetWebResponseAsync("http://baidu.com");      Console.WriteLine("jxqlovejava");      Console.Read();    }  }}