C# 使用XPath解析网页

// From File
var doc = new HtmlDocument();
doc.Load(filePath);

// From String
var doc = new HtmlDocument();
doc.LoadHtml(html);

// From Web
var url = "http://html-agility-pack.net/";
var web = new HtmlWeb();
var doc = web.Load(url);

//XPath
var nodes = doc.DocumentNode.SelectNodes("//*[@id=\"body\"]");

static void Main(string[] args)
 
{
 
    try {
 
        WebClient MyWebClient = new WebClient();
 
        
        MyWebClient.Credentials = CredentialCache.DefaultCredentials;//获取或设置用于向Internet资源的请求进行身份验证的网络凭据
 
        Byte[] pageData = MyWebClient.DownloadData(“http://www.163.com”); //从指定网站下载数据
 
        string pageHtml = Encoding.Default.GetString(pageData);  //如果获取网站页面采用的是GB2312，则使用这句            
 
        //string pageHtml = Encoding.UTF8.GetString(pageData); //如果获取网站页面采用的是UTF-8，则使用这句
 
        Console.WriteLine(pageHtml);//在控制台输入获取的内容
 
        using (StreamWriter sw = new StreamWriter("c:\\test\\ouput.html"))//将获取的内容写入文本
 
        {
 
            sw.Write(pageHtml);
 
        }
 
        Console.ReadLine();             
 
    }
 
    catch(WebException webEx) {
 
        Console.WriteLine(webEx.Message.ToString());
 
    }
 
}

WebBrowser web = new WebBrowser(); 
web.Navigate("http://www.xjflcp.com/ssc/"); 
web.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(web_DocumentCompleted); 
void web_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) 
        { 
            WebBrowser web = (WebBrowser)sender; 
            HtmlElementCollection ElementCollection = web.Document.GetElementsByTagName("Table"); 
            foreach (HtmlElement item in ElementCollection) 
            { 
                 File.AppendAllText("Kaijiang_xj.txt", item.InnerText); 
            } 
        }

HttpWebRequest httpReq; 
HttpWebResponse httpResp; 
 
string strBuff = ""; 
char[] cbuffer = new char[256]; 
int byteRead = 0; 
 
string filename = @"c:\log.txt"; 
///定义写入流操作 
public void WriteStream() 
{ 
Uri httpURL = new Uri(txtURL.Text);
 
///HttpWebRequest类继承于WebRequest，并没有自己的构造函数，需通过WebRequest的Creat方法 建立，并进行强制的类型转换 
      httpReq = (HttpWebRequest)WebRequest.Create(httpURL); 
///通过HttpWebRequest的GetResponse()方法建立HttpWebResponse,强制类型转换
 
   httpResp = (HttpWebResponse) httpReq.GetResponse(); 
///GetResponseStream()方法获取HTTP响应的数据流,并尝试取得URL中所指定的网页内容
 
     ///若成功取得网页的内容，则以System.IO.Stream形式返回，若失败则产生ProtoclViolationException错 误。在此正确的做法应将以下的代码放到一个try块中处理。这里简单处理 
Stream respStream = httpResp.GetResponseStream();
 
///返回的内容是Stream形式的，所以可以利用StreamReader类获取GetResponseStream的内容，并以
 
StreamReader类的Read方法依次读取网页源程序代码每一行的内容，直至行尾（读取的编码格式：UTF8） 
StreamReader respStreamReader = new StreamReader(respStream,Encoding.UTF8);
 
byteRead = respStreamReader.Read(cbuffer,0,256); 
 
while (byteRead != 0) 
{ 
string strResp = new string(cbuffer,0,byteRead); 
                  strBuff = strBuff + strResp; 
                  byteRead = respStreamReader.Read(cbuffer,0,256); 
} 
 
respStream.Close(); 
txtHTML.Text = strBuff; 
}