C# 如何在Html敏捷包中获得重定向URL
我想解析集合URL中的所有URL。我找到了以下方法:C# 如何在Html敏捷包中获得重定向URL,c#,parsing,redirect,href,html-agility-pack,C#,Parsing,Redirect,Href,Html Agility Pack,我想解析集合URL中的所有URL。我找到了以下方法: public static List<string> ParseLinks(string urlToCrawl) { WebClient webClient = new WebClient(); byte[] data = webClient.DownloadData(urlToCrawl); string download = Encoding.ASCII.GetStr
public static List<string> ParseLinks(string urlToCrawl)
{
WebClient webClient = new WebClient();
byte[] data = webClient.DownloadData(urlToCrawl);
string download = Encoding.ASCII.GetString(data);
HashSet<string> list = new HashSet<string>();
var doc = new HtmlDocument();
doc.LoadHtml(download);
HtmlNodeCollection nodes = doc.DocumentNode.SelectNodes("//a[@href]");
foreach (var n in nodes)
{
string href = n.Attributes["href"].Value;
list.Add(GetAbsoluteUrlString(urlToCrawl, href));
}
return list.ToList();
}
static string GetAbsoluteUrlString(string baseUrl, string url)
{
var uri = new Uri(url, UriKind.RelativeOrAbsolute);
if (!uri.IsAbsoluteUri)
uri = new Uri(new Uri(baseUrl), uri);
return uri.ToString();
}
公共静态列表解析链接(字符串urlToCrawl)
{
WebClient WebClient=新的WebClient();
字节[]数据=webClient.DownloadData(urlToCrawl);
字符串下载=Encoding.ASCII.GetString(数据);
HashSet list=新的HashSet();
var doc=新的HtmlDocument();
doc.LoadHtml(下载);
HtmlNodeCollection nodes=doc.DocumentNode.SelectNodes(“//a[@href]”);
foreach(节点中的变量n)
{
字符串href=n.Attributes[“href”].Value;
添加(GetAbsoluteUrlString(urlToCrawl,href));
}
return list.ToList();
}
静态字符串GetAbsoluteUrlString(字符串baseUrl、字符串url)
{
var uri=新的uri(url,UriKind.RelativeOrAbsolute);
如果(!uri.IsAbsoluteUri)
uri=新uri(新uri(baseUrl),uri);
返回uri.ToString();
}
一切都很好,但在一些网站上,链接通过他们的网站(他们重定向)。我有一个链接:。当我想使用我的方法提取链接时,ParseLinks方法会给我错误的URL,比如。。。我的期望是。。。因为当我们转到上面的链接时,它会重定向到。那么,如何从当前URL获取重定向页面?请给我一些解决问题的办法 我用几个关键词做了一些研究,找到了解决问题的方法。以下方法解决了我的问题:
public static string GetFinalRedirect(string url)
{
if(string.IsNullOrWhiteSpace(url))
return url;
int maxRedirCount = 8; // prevent infinite loops
string newUrl = url;
do
{
HttpWebRequest req = null;
HttpWebResponse resp = null;
try
{
req = (HttpWebRequest) HttpWebRequest.Create(url);
req.Method = "HEAD";
req.AllowAutoRedirect = false;
resp = (HttpWebResponse)req.GetResponse();
switch (resp.StatusCode)
{
case HttpStatusCode.OK:
return newUrl;
case HttpStatusCode.Redirect:
case HttpStatusCode.MovedPermanently:
case HttpStatusCode.RedirectKeepVerb:
case HttpStatusCode.RedirectMethod:
newUrl = resp.Headers["Location"];
if (newUrl == null)
return url;
if (newUrl.IndexOf("://", System.StringComparison.Ordinal) == -1)
{
// Doesn't have a URL Schema, meaning it's a relative or absolute URL
Uri u = new Uri(new Uri(url), newUrl);
newUrl = u.ToString();
}
break;
default:
return newUrl;
}
url = newUrl;
}
catch (WebException)
{
// Return the last known good URL
return newUrl;
}
catch (Exception ex)
{
return null;
}
finally
{
if (resp != null)
resp.Close();
}
} while (maxRedirCount-- > 0);
return newUrl;
}