HTML Agility Pack选择节点

Question

我正在尝试使用HTML Agility包从站点中抓取一些数据.我真的在努力弄清楚如何在foreach中使用selectnodes,然后将数据导出到列表或数组.

这是我到目前为止使用的代码.

       string result = string.Empty;

        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(http://www.amazon.com/gp/offer-listing/B002UYSHMM/);
        request.Method = "GET";

        using (var stream = request.GetResponse().GetResponseStream())
        using (var reader = new StreamReader(stream, Encoding.UTF8))
        {
            result = reader.ReadToEnd();
        }

        HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
        doc.Load(new StringReader(result));
        HtmlNode root = doc.DocumentNode;

        string itemdesc = doc.DocumentNode.SelectSingleNode("//h1[@class='producttitle']").InnerText;  //this works perfectly to get the title of the item
        //HtmlNodeCollection sellers = doc.DocumentNode.SelectNodes("//id['bucketnew']/div/table/tbody/tr/td/ul/a/img/@alt");//this does not work at all in getting the alt attribute from the seller images
        HtmlNodeCollection prices = doc.DocumentNode.SelectNodes("//span[@class='price']"); //this works fine getting the prices
        HtmlNodeCollection nodes = doc.DocumentNode.SelectNodes("//div[@class='resultsset']/table/tbody[@class='result']/tr"); //this is the code I am working on to try to collect each tr in the result.  I then want to eather add each span.price to a list from this and also add each alt attribute from the seller image to a list.  Once I get this working I will want to use an if statement in the case that there is text for the seller name instead of an image.

        List<string> sellers = new List<string>();
        List<string> prices = new List<string>();

        foreach (HtmlNode node in nodes)
        {
            HtmlNode seller = node.SelectSingleNode(".//img/@alt");  // I am not sure if this works
            sellers.Add(seller.SelectSingleNode("img").Attributes["alt"]); //this definitly does not work and will not compile.

        }

我在上面的代码中有评论显示哪些有效,哪些无效,以及我想要完成的内容.

如果有人有任何建议或阅读将是伟大的!我一直在搜索论坛和示例,并没有遇到任何我可以使用的东西.

Answer 1

注释掉的第一个问题SelectNodes不起作用,因为'id'不是元素名称,它是属性名称.您已在其他表达式中使用了正确的语法来选择属性并比较该值.例如,//ElementName[@attributeName='value'].我认为即使[attributeName='value']应该工作,但我还没有测试过.

SelectNodes函数内部的语法称为"XPath".此链接可能会帮助您.

seller您选择的节点是node当前迭代的兄弟,它是带有alt属性的img.但是我认为你想要的正确语法就是img[@alt].

你说它不会编译的下一个问题,检查错误信息,它可能会抱怨参数类型.sellers.Add我想要命名另一个HtmlNode,而不是一个属性,这是add里面的表达式返回的.

另外,查看Html Agility包文档以及有关语法的其他问题.