Getting text between all tags in a given html and recursively going through links

问题

i have checked a couple of posts on stack overflow regarding getting all the words between all the html tags! All of them confused me up! some people recommend regular expression specifically for a single tag while some have mentioned parsing techniques! am basically trying to make a web crawler! for that i have got the html of the link i fetched to my program in a string! i have also extracted the links from the html that i stored in my data string! now i want to crawl through the depth and extract words on the page of all links i extracted from my string! i got two questions! how can i fetch the words on the each of the web pages ignoring tags and java script? secondly how would i recursively crawl through the links??

This is how am getting html in the string:

public void getting_html_code_of_link()
    {
        string urlAddress = "http://google.com";

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(urlAddress);
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        if (response.StatusCode == HttpStatusCode.OK)
        {
            Stream receiveStream = response.GetResponseStream();
            StreamReader readStream = null;
            if (response.CharacterSet == null)
                readStream = new StreamReader(receiveStream);
            else
                readStream = new StreamReader(receiveStream, Encoding.GetEncoding(response.CharacterSet));
            data = readStream.ReadToEnd();
            response.Close();
            readStream.Close();
            Console.WriteLine(data);
        }
    }

and this is how am extracting link refrences from the url i give:

public void regex_ka_kaam()
    {
        StringBuilder sb = new StringBuilder();
        //Regex hrefs = new Regex("<a href.*?>");
        Regex http = new Regex("http://.*?>");

        foreach (Match m in http.Matches(data))
        {
            sb.Append(m.ToString());
            if (http.IsMatch(m.ToString()))
            {

                sb.Append(http.Match(m.ToString()));
                sb.Append("                                                                        ");
                //sb.Append("<br>");
            }
            else
            {
                sb.Append(m.ToString().Substring(1, m.ToString().Length - 1)); //+ "<br>");
            }
        }
        Console.WriteLine(sb);
    }

回答1:

Regex is not a good choice for parsing HTML files..

HTML is not strict nor is it regular with its format..

Use htmlagilitypack

---

This extracts all the links from the web page

public List<string> getAllLinks(string webAddress)
{
    HtmlAgilityPack.HtmlWeb web = new HtmlAgilityPack.HtmlWeb();
    HtmlDocument newdoc=web.Load(webAddress);

    return doc.DocumentNode.SelectNodes("//a[@href]")
              .Where(y=>y.Attributes["href"].Value.StartsWith("http"))
              .Select(x=>x.Attributes["href"].Value)
              .ToList<string>();
}

---

this gets all the content excluding tags in the html

public string getContent(string webAddress)
{
    HtmlAgilityPack.HtmlWeb web = new HtmlAgilityPack.HtmlWeb();
    HtmlDocument doc=web.Load(webAddress);

    return string.Join(" ",doc.DocumentNode.Descendants().Select(x=>x.InnerText));
}

---

this crawls through all the links

public void crawl(string seedSite)
{
        getContent(seedSite);//gets all the content
        getAllLinks(seedSite);//get's all the links
}

来源：https://stackoverflow.com/questions/13662267/getting-text-between-all-tags-in-a-given-html-and-recursively-going-through-link