TPL使用异步编程模型(APM)实现简单网页抓取

using System;using System.Collections.Generic;using System.Linq;using System.Net;using System.Threading;using System.Threading.Tasks;namespace fofo.NetSpider{    public class SimpleNetSpider    {        public void Start()        {            string[] urls = InitUrls();            Task<WebResponse>[] tasks = urls.Select(url => GetResponseAsync(url)).ToArray();            Task.WaitAll(tasks);        }        private string[] InitUrls()        {            string[] urls =             {                "http://www.baidu.com/",                "http://www.cnblogs.com",                "http://www.csdn.com"            };            return urls;        }        // 启动任务        private Task<WebResponse> GetResponseAsync(string strUrl)        {            WebRequest webRequest = WebRequest.Create(strUrl);            Task<WebResponse> task = Task<WebResponse>.Factory.FromAsync(webRequest.BeginGetResponse, GetResponseAsyncCompleted, webRequest);            return task;        }        // 抓取结束回调函数        private WebResponse GetResponseAsyncCompleted(IAsyncResult result)        {            WebRequest webRequest = (WebRequest)result.AsyncState;            WebResponse response = webRequest.EndGetResponse(result);            using (System.IO.StreamReader reader = new System.IO.StreamReader(response.GetResponseStream()))            {                // 具体处理                        }            return response;        }       }}