多线程的一点东西。。

毕业设计准备做搜索方面，所以开始写爬虫程序，想法是这样，从一个网站开始，抓内容，分析页面，获取页面所有链接，将链接放到UrlList列表，然后索引，一直不断循环。这星期一直在学习多线程，下面是抓取页面内容的代码，先做个备忘先。

开始事件，以及线程函数

        private void Start_Click(object sender, EventArgs e)
        {
            startUrl = StartUrl.Text.Trim();
            //获取网页内容的线程数
            if (!string.IsNullOrEmpty(ThreadCount.Text.Trim()))
            {
                threadCount = int.Parse(ThreadCount.Text.Trim());
            }
            else
            {
                threadCount = 1;
            }
            //获取链接线程数
            if (!string.IsNullOrEmpty(GetUrlThreadCount.Text.Trim()))
            {
                getUrlThreadCount = int.Parse(GetUrlThreadCount.Text.Trim());
            }
            else
            {
                getUrlThreadCount = 1;
            }

            if (startUrl == null)
            {
                MessageBox.Show("请输入链接地址");
                return;
            }
            else
            {
                Regex re = new Regex(@"http(s)?://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?");
                if (!re.Match(startUrl).Success)
                {
                    MessageBox.Show("链接格式错误");
                    return;
                }
                else
                {
                    urllist.Url.Add(startUrl);
                    urllist.IsDownload.Add(Encrypt.MD5EncryptStr(startUrl),0);
                }
            }


            urllist.Url.Add("http://www.hao123.com");
            urllist.IsDownload.Add(Encrypt.MD5EncryptStr("http://www.hao123.com"), 0);

            urllist.Url.Add("http://www.zhku.com");
            urllist.IsDownload.Add(Encrypt.MD5EncryptStr("http://www.zhku.com"), 0);

            urllist.Url.Add("http://www.sina.com");
            urllist.IsDownload.Add(Encrypt.MD5EncryptStr("http://www.sina.com"), 0);

            urllist.Url.Add("http://www.zhku.edu.cn");
            urllist.IsDownload.Add(Encrypt.MD5EncryptStr("http://www.zhku.edu.cn"), 0);

            urllist.Url.Add("http://www.39.net");
            urllist.IsDownload.Add(Encrypt.MD5EncryptStr("http://www.39.net"), 0);

            urllist.Url.Add("http://www.cnblogs.com");
            urllist.IsDownload.Add(Encrypt.MD5EncryptStr("http://www.cnblogs.com"), 0);

            urllist.Url.Add("http://www.google.com");
            urllist.IsDownload.Add(Encrypt.MD5EncryptStr("http://www.google.com"), 0);

            Thread[] threadPool = new Thread[threadCount];
            int count=3;

            for (int i = 0; i < count; i++)
            {
                threadPool[i] = new Thread(new ParameterizedThreadStart(GetPageContent));
                threadPool[i].Start(i);
            }

                       while (true)
            {
                if (!threadPool[0].IsAlive && !threadPool[1].IsAlive && !threadPool[2].IsAlive)
                {
                    listBox1.DataSource = PageContentList.PageContents;
                    threadPool[0].Abort();
                    threadPool[1].Abort();
                    threadPool[2].Abort();
                    break;
                }
            }
        }

        public void GetPageContent(object startindex)
        {
            int start = (int)startindex;
            lock(urllist)
            {
                Monitor.Enter(urllist);
                int n = 0;
                if (urllist.IsDownload.Count < threadCount)
                {
                    n = urllist.IsDownload.Count;
                }
                else
                {
                    n = threadCount;
                }
                for (int i = start; i < urllist.IsDownload.Count; i = i + n)
                {
                    if (i > urllist.IsDownload.Count)
                    {
                        break;
                    }
                    string key = Encrypt.MD5EncryptStr(urllist.Url[i]);
                    
                    if ((int)urllist.IsDownload[key] == 0)
                    {
                        urllist.IsDownload[key] = 1;
                        string sb = null;

                        WebClient client = new WebClient();
                        Byte[] read = new Byte[1024];
                        read = client.DownloadData(urllist.Url[i].Trim().ToString());

                        System.Text.Encoding encoder = System.Text.Encoding.GetEncoding("GB2312");
                        sb += encoder.GetString(read, 0, read.Length);

                        lock (PageContentList)
                        {
                            Monitor.Enter(PageContentList);
                            PageContentList.PageContents.Add(sb);
                            PageContentList.IsAnalyse.Add(Encrypt.MD5EncryptStr(sb), 0);
                            PageContentList.IsIndexed.Add(Encrypt.MD5EncryptStr(sb), 0);
                            Monitor.Pulse(PageContentList);
                            Monitor.Exit(PageContentList);
                        }
                    }
                }
                Monitor.Pulse(urllist);
                Monitor.Exit(urllist);
            }
            Thread.Sleep(500);
        }

链接列表类，页面内容类

    public class UrlList
    {
        private List<string> url = new List<string>();
        private Hashtable isDownload = new Hashtable();

        /// <summary>
        /// 下载链接
        /// </summary>
        public List<string> Url
        {
            get { return url; }
            set { url = value; }
        }

        /// <summary>
        /// 是否为已下载链接0为否，1为是
        /// </summary>
        public Hashtable IsDownload
        {
            get { return isDownload; }
            set { isDownload = value; }
        }
    }

    public class PageContent
    {
        private List<string> pageContents = new List<string>();
        private Hashtable isAnalyse = new Hashtable();
        private Hashtable isIndexed = new Hashtable();

        /// <summary>
        /// 页面内容列表
        /// </summary>
        public List<string> PageContents
        {
            get { return pageContents; }
            set { pageContents = value; }
        }
        /// <summary>
        /// 是否分析了页面，0为否，1为是
        /// </summary>
        public Hashtable IsAnalyse
        {
            get { return isAnalyse; }
            set { isAnalyse = value; }
        }
        /// <summary>
        /// 是否对页面进行索引，0为否，1为是
        /// </summary>
        public Hashtable IsIndexed
        {
            get { return isIndexed; }
            set { isIndexed = value; }
        }
    }

上面的页面都可以抓取到，可是点击开始后就好卡，不知道什么原因，各路高人帮忙看看，指点一下。小弟感激不尽！