Hi Charts,
From your description, you're writing a custom web page spider and
wondering how to deal with button and hyperlinks appear on the page ,
correct?
Based on my understanding, web spider just retrieve the html content of web
pages and parse the elements in it. For button or hyperlinks elements, I
think they'll rely on the following facts:
1. Hyperlink is just a linker point to another external resource, so how
are you parsing the main page(use WebRequest?), you can just retrieve the
"href" location attribute from the hyperlink and use
WebRequest(sequentially or start in a new thread) to visit the linked page.
2. For Button, I think it's more complex. Depend on what does the button
do, if it just submit the page, you need to check the <form> tag's "Action"
url, and use WebRequest to visit the resource in the "Action' attribute. If
it just perform a postback (to self page) like ASP.NET, I don't think you
need to do additional work. Also, some button's click may depend on some
other entry fields on the page, it is not quite possible to cover all kinds
of page's action logic in spider code.
BTW, what component are you use to parse html content? I've used the Html
Agility Pack which is a pure .net based library and it's quite useful:
#Html Agility Pack
http://www.codeplex.com/htmlagilitypack
Here are some other good tech aritcles about writing a custom Web Spider:
#MyDownloader: A Multi-thread C# Segmented Download Manager
http://www.codeproject.com/KB/IP/MyDownloader.aspx?fid=475780&df=90&mpp=25&n
oise=3&sort=Position&view=Quick&fr=51
#A Web Spider Library in C#
http://www.codeproject.com/KB/aspnet/ZetaWebSpider.aspx
Sincerely,
Steven Cheng
Microsoft MSDN Online Support Lead
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