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获取网页的HTML，大致有三种方法：1. 通过WebClient下载网页；2. 通过HttpWebRequest和HttpWebResponse获得网页的HTML；3. 通过微软提供的WebBrowser控件获得网页的Document Tree。解析HTML，主要方法有两种：正则表达式和Document Tree。以下分别给予简要介绍。

    本文只给出大致的实现思路，代码也较为简洁，只对各个思路给出简单的解释说明。

    预备知识：要获得网页的HTML，首先需要对HTTP协议中的Get和Post方法有简单的了解。Get方法是通过Uri向服务器提交请求，服务器根据Uri中指定的参数对客户端请求进行响应，返回请求的数据；而Post请求一般需要将提交的数据放到请求报文的body部分，还需要在报文首部Content-Length字段中指出body的长度，服务器收到Post请求后，在对这些请求数据进行处理后，再返回相应的响应数据。

    方法1：

    WebClient wClient = new WebClient();
    byte[] pageData = wClient.DownloadData("http://www.17aspx.com/");
    string html = Encoding.UTF8.GetString(pageData);

    方法2：

    HttpWebRequest request = HttpWebRequest.Create("http://www.17aspx.com/") as HttpWebRequest;
    request.Method = "GET";    
    HttpWebResponse response = request.GetResponse() as HttpWebResponse;
    Stream stream = response.GetResponseStream();
    StreamReader reader = new StreamReader(stream, Encoding.UTF8);
    string html = reader.ReadToEnd();
    reader.Close();

    方法3：

    WebBrowser.Navigate("http://www.17aspx.com/", .....);

    然后在WebBrowser的NavigateComplete事件中，得到Document Tree，就可以对网页的HTML进行处理了。    对于Post方法，只需要在调用获得响应的方法前写入需要post的数据即可：

 1: string url = "http://www.ups.com/WebTracking/track";

 2: string postData = "loc=zh_cn&HTMLVersion=5.0&saveNumbers=null&trackNums 

 3: =1ZX580116610381498&AgreeToTermsAndConditions=yes&track.x=17&track.y=4";

 4: string html = "";

 5: Encoding encode = Encoding.GetEncoding("GB2312");

 6: byte[] data = encode.GetBytes(postData);

 7: HttpWebRequest req = WebRequest.Create(url) as HttpWebRequest;

 8: req.AllowAutoRedirect = true;

 9: req.Method = "POST";

 10: req.ContentType = "application/x-www-form-urlencoded";

 11: req.ContentLength = data.Length; // 要Post的数据的长度 

 12:   

 13: // 把要Post的Data写入(追加)到outStream对象中，使其具有post data 

 14: Stream outStream = req.GetRequestStream();

 15: outStream.Write(data, 0, data.Length);

 16: outStream.Close();

 17:   

 18: // Send Request and get the response 

 19: HttpWebResponse response = req.GetResponse() as HttpWebResponse;

 20:   

 21: // 得到response的流 

 22: Stream responseStream = response.GetResponseStream();

 23: StreamReader sr = new StreamReader(responseStream, encode);

 24:   

 25: html = sr.ReadToEnd();

 26: sr.Close();