HttpWebRequest command to get directory listing
In the following post I followed the examples to create my httprequest and list files from webServer directory: C# HttpWebRequest command to get directory listing
I'm trying to use the example there to list files from my web server. I can list the files from the example server quoted on the link, but my server just shows the last added file. My code is exactly like the example ther开发者_如何学Goe. I noticed that my html code is a little different. Someone have an idea:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>186.215.156.154 - /download/Zatix/Zatix - Satisfação Geral/</title>
</head>
<body>
<h1>
186.215.156.154 - /download/Zatix/Zatix - Satisfação Geral/</h1>
<hr>
<pre>
<a href="/download/Zatix/">[Para a pasta superior]</a>
<br>
<br>
sexta-feira, 19 de novembro de 2010 11:17 52355 <a href="/download/Zatix/Zatix%20-%20Satisfa%C3%A7%C3%A3o%20Geral/Zatix%20-%20Satisfa%C3%A7%C3%A3o%20Geral_3_00.zip">Zatix - Satisfação Geral_3_00.zip</a><br>sexta-feira, 19 de novembro de 2010 11:17 52355 <a href="/download/Zatix/Zatix%20-%20Satisfa%C3%A7%C3%A3o%20Geral/Zatix%20-%20Satisfa%C3%A7%C3%A3o%20Geral_4_00.zip">Zatix - Satisfação Geral_4_00.zip</a>
<br>
</pre>
<hr>
</body>
</html
I think I have to change something in the return of GetDirectoryListingRegexForUrl method.
My code is something like this:
private string GetDirectoryListingRegexForUrl(string url)
{
if (url.Equals(Url));
{
return "<A HREF=\".*\">(?<name>.*)</A>";
}
throw new NotSupportedException();
}
public void ListStudies()
{
Url = BaseUrl + this.clientName + "/" + this.activeStudy + "/";
Console.WriteLine(Url);
CookieContainer cookies;
HttpWebResponse response;
HttpWebRequest req = (HttpWebRequest)System.Net.WebRequest.Create(Url);
req.Credentials = _NetworkCredential;
req.CookieContainer = new CookieContainer();
req.AllowAutoRedirect = true;
cookies = req.CookieContainer;
try
{
response = (HttpWebResponse)req.GetResponse();
if (response.StatusCode != HttpStatusCode.OK)
Console.WriteLine("URL NÃO RESPONDEU");
else
Console.WriteLine("URL OK");
using (response)
{
using (StreamReader reader = new StreamReader(response.GetResponseStream()))
{
string html = reader.ReadToEnd();
Regex regex = new Regex(GetDirectoryListingRegexForUrl(Url));
MatchCollection matches = regex.Matches(html);
if (matches.Count > 0)
{
foreach (Match match in matches)
{
if (match.Success)
{
Console.WriteLine(match.Groups["name"]);
}
}
}
}
}
}
catch (Exception e)
{
MessageBox.Show(e.Message, "Update Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
I hope you can help me! Thanks.
Two major problems here.
1). The output of a request like this is completely arbitrary and not even guaranteed. It's the server's concern.
2). Regex is not a suitable means for parsing HTML or any similar structure because it is not a regular grammar. Your best bet assuming you have any kind of reliability in your response at all is to rely on something like the HtmlAgilityPack to enforce a rigourous XHTML document (may not be required if you're lucky) and read that as an XML document with XPath queries to pull out the content you're interested in.
Here's the correct regex:
<A HREF=\".*?\">(?<name>.*?)</A>
Compare it to the original one:
<A HREF=\".*\">(?<name>.*)</A>
The problem lies with the repetition operators .* which are greedy by default. Greedy means the regex will expand as far as possible while looking for a match. Meaning it will start with the first <A and finishing with the last A> in the string letting everything in between in. That 'everything' includes the others <A...A>'s in the middle.
You need to specify that the repetition operators are lazy. You do it by adding ? to them like .*?.
P.S. Parsing HTML with regular expressions is notoriously a bad idea. It's okay if you need a quick and dirty fix but a no-go for a long-term solution. Add to that the fact that in your case the output will vary per server and likely per-server version. The code is not universally-functional. Please consider the other approach like negotiating with the server directly to get a directory listing (if you have the access of course).
And finally some funny read to the thema:
Parsing Html The Cthulhu Way
RegEx match open tags except XHTML self-contained tags
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