Thursday, December 18, 2008

Windows Forms + Web, WIB part II


A while back I made the case for applications that put together the strengths of Windows Forms and Web technologies (I thought of the catchy "WIB" as a name for this approach). The example I’d given then was a Windows Forms hosted Web Browser for local images that one could use for annotation that leveraged Windows for local file storage and a Web technology like jQuery for doing transitions in the user interface.

Today I thought of another use for this approach that wrapped itself nicely into a tool I've been using for some time to download mp3s from a given website1,2. I call the tool "Fortinbras" and if you find it useful I'd be delighted.

So how was Fortinbras changed?

Parsing the HTML for mp3 files was a little tricky. My initial approach was to use a regular expression against the text of the document which, truth be told, is a brittle approach. Part of why I never trumpted the tool was because I never completely perfected this tactic (while it worked well enough for me personally). My code looked as follows:

	WebClient wc = new WebClient();
string pageText = wc.DownloadString(browser.Url.ToString());
Regex re = new Regex("href=\"(?<url>.+?mp3)\"", RegexOptions.IgnoreCase);
Match mp3Matches = re.Match(text);
while (mp3Matches.Success)
string matchUrl = mp3Matches.Groups["url"].Value.ToString();
AddMp3(browser.Url.ToString(), data, matchUrl);
mp3Matches = mp3Matches.NextMatch();

Today my epiphany was that I didn't need to use a regular expression when I could use the DOM from Windows Forms to pull out the anchors that have mp3 destinations. Here's what that looks like:

	while (browser.Document.Body == null)Application.DoEvents();
HtmlElementCollection anchors = browser.Document.Body.GetElementsByTagName("a");
foreach (HtmlElement anch in anchors)
string linkUrl = anch.GetAttribute("href");
if (linkUrl.ToLower().EndsWith("mp3"))
AddMp3(browser.Url.ToString(), data, linkUrl);

As usual feedback is welcome - you can download a copy of the Fortinbras project here.

1I am aware of the Firefox extensions that do this but someday (imagine a pie in the sky look on my face) I was hoping to incorporate a "favorites" list with URLs / locations so that this would be a one stop shop for my downloading and organizing of podcasts. My goal here is embarrasment driven development so I'll probably be bummed enough about the code I've just posted to put in some enhancements as time permits.

2My friend's music blog is a great stop, try a couple of tracks at The Look Back.


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