C# 从 wiki 页面抓取数据（屏幕抓取）

Question

我想抓取一个 Wiki 页面。具体来说，this one.

我的应用程序将允许用户输入车辆的注册号（例如，SBS8988Z），它会显示相关信息（在页面上）。

例如，如果用户在我的应用程序的文本字段中输入 SBS8988Z，它应该在该 wiki 页面上查找该行

SBS8988Z (SLBP 192/194*) - F&N NutriSoy Fresh Milk: Singapore's No. 1 Soya Milk! (2nd Gen)

并返回 SBS8988Z (SLBP 192/194*) - F&N NutriSoy 鲜奶：新加坡排名第一的豆浆！ （第二代）。

到目前为止，我的代码是（从各个网站复制和编辑的）...

WebClient getdeployment = new WebClient();
string url = "http://sgwiki.com/wiki/Scania_K230UB_(Batch_1_Euro_V)";

getdeployment.Headers["User-Agent"] = "NextBusApp/GetBusData UserAgent";
string sgwikiresult = getdeployment.DownloadString(url); // <<< EXCEPTION
MessageBox.Show(sgwikiresult); //for debugging only!

HtmlAgilityPack.HtmlDocument sgwikihtml = new HtmlAgilityPack.HtmlDocument();
sgwikihtml.Load(new StreamReader(sgwikiresult));
HtmlNode root = sgwikihtml.DocumentNode;

List<string> anchorTags = new List<string>();   

foreach(HtmlNode deployment in root.SelectNodes("SBS8988Z"))
{
    string att = deployment.OuterHtml;
    anchorTags.Add(att);
}

但是，我收到了一个 ArgumentException 未处理 - 路径中有非法字符。

代码有什么问题？有没有更简单的方法来做到这一点？我正在使用 HtmlAgilityPack，但如果有更好的解决方案，我很乐意遵守。

Answer 1

代码有什么问题？坦率地说，一切。 :P

该页面的格式与您阅读时的方式不同。你不能希望以这种方式获得所需的内容。

页面的内容（我们感兴趣的部分）看起来像这样：

<h2>
<span id="Deployments" class="mw-headline">Deployments</span>
</h2>
<p>
    <!-- ... -->
    <b>SBS8987B</b>
    (SLBP 192/194*)
    <br>
    <b>SBS8988Z</b>
    (SLBP 192/194*) - F&amp;N NutriSoy Fresh Milk: Singapore's No. 1 Soya Milk! (2nd Gen)
    <br>
    <b>SBS8989X</b>
    (SLBP SP)
    <br>
    <!-- ... -->
</p>

基本上我们需要找到包含我们要查找的注册号的b 元素。一旦我们找到该元素，获取文本并将其放在一起形成结果。代码如下：

static string GetVehicleInfo(string reg)
{
    var url = "http://sgwiki.com/wiki/Scania_K230UB_%28Batch_1_Euro_V%29";

    // HtmlWeb is a helper class to get pages from the web
    var web = new HtmlAgilityPack.HtmlWeb();

    // Create an HtmlDocument from the contents found at given url
    var doc = web.Load(url);

    // Create an XPath to find the `b` elements which contain the registration numbers
    var xpath = "//h2[span/@id='Deployments']" // find the `h2` element that has a span with the id, 'Deployments' (the header)
              + "/following-sibling::p[1]"     // move to the first `p` element (where the actual content is in) after the header
              + "/b";                          // select the `b` elements

    // Get the elements from the specified XPath
    var deployments = doc.DocumentNode.SelectNodes(xpath);

    // Create a LINQ query to find the  requested registration number and generate a result
    var query =
        from b in deployments                 // from the list of registration numbers
        where b.InnerText == reg              // find the registration we're looking for
        select reg + b.NextSibling.InnerText; // and create the result combining the registration number with the description (the text following the `b` element)

    // The query should yield exactly one result (or we have a problem) or none (null)
    var content = query.SingleOrDefault();

    // Decode the content (to convert stuff like "&" to "&")
    var decoded = System.Net.WebUtility.HtmlDecode(content);

    return decoded;
}