XML：使用C＃搜索特定文本的元素

Question

I'm trying to get a list of PDF links from different websites. First I'm using the Web client class to download the page source. I then use sgmlReader to convert the HTML to XML. So for one particular site, I'll get a tag that looks like this:

<p><a href="pub/1985_to_1997_Board_Action_Summary.pdf">1985 to 1997 Board Action Summary</a></p>

I need to grab all the links that contain ".pdf". Obviously not all websites are laid out the same, so just searching for a <p> tag, wont be dynamic enough. I'd rather not use linq, but I will if I have to. Thanks in advance.

Answer 1

Linq makes this easy...

var hrefs = doc.Root.Descendants("a")
    .Where(a => a.Attrib("href").Value.ToUpper().EndsWith(".PDF"))
    .Select(a => a.Attrib("href"));

away you go! (note: did this from memory, so you might have to fix it somewhat)

This will break down for <a/> tags that don't have an href (anchors) but you can fix that surely...

Answer 2

I think you have 2 options here. If you need only the links, you can use Regular Expressions to find the matches for strings ending with .pdf. If you need to manipulate the XML structure or get other values from the XML, it would be better to use XmlDocument and use an XPath query to find out the nodes which have a link to a pdf file in it. Using LINQ to XML just reduces the number of lines of code you have to write.