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C# Convert Relative to Absolute Links in HTML String

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余生分开走
余生分开走 2020-12-16 04:03

I\'m mirroring some internal websites for backup purposes. As of right now I basically use this c# code:

System.Net.WebClient client = new System.Net.WebCli
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  • 醉话见心
    2020-12-16 04:35

    While this may not be the most robust of solutions it should get the job done.

    var host = "http://domain.is";
var someHtml = @"
<a href=""/some/relative"">Relative</a>
<img src=""/some/relative"" />
<a href=""http://domain.is/some/absolute"">Absolute</a>
<img src=""http://domain.is/some/absolute"" />
";


someHtml = someHtml.Replace("src=\"" + host,"src=\"");
someHtml = someHtml.Replace("href=\"" + host,"src=\"");
someHtml = someHtml.Replace("src=\"","src=\"" + host);
someHtml = someHtml.Replace("href=\"","src=\"" + host);
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  • 北海茫月
    2020-12-16 04:36

    this is what you are looking for, this code snippet can convert all the relative URLs to absolute inside any HTML code: 

    Private Function ConvertALLrelativeLinksToAbsoluteUri(ByVal html As String, ByVal PageURL As String)
    Dim result As String = Nothing
    ' Getting all Href
    Dim opt As New RegexOptions
    Dim XpHref As New Regex("(href="".*?"")", RegexOptions.IgnoreCase)
    Dim i As Integer
    Dim NewSTR As String = html
    For i = 0 To XpHref.Matches(html).Count - 1
        Application.DoEvents()
        Dim Oldurl As String = Nothing
        Dim OldHREF As String = Nothing
        Dim MainURL As New Uri(PageURL)
        OldHREF = XpHref.Matches(html).Item(i).Value
        Oldurl = OldHREF.Replace("href=", "").Replace("HREF=", "").Replace("""", "")
        Dim NEWURL As New Uri(MainURL, Oldurl)
        Dim NewHREF As String = "href=""" & NEWURL.AbsoluteUri & """"
        NewSTR = NewSTR.Replace(OldHREF, NewHREF)
    Next
    html = NewSTR
    Dim XpSRC As New Regex("(src="".*?"")", RegexOptions.IgnoreCase)
    For i = 0 To XpSRC.Matches(html).Count - 1
        Application.DoEvents()
        Dim Oldurl As String = Nothing
        Dim OldHREF As String = Nothing
        Dim MainURL As New Uri(PageURL)
        OldHREF = XpSRC.Matches(html).Item(i).Value
        Oldurl = OldHREF.Replace("src=", "").Replace("src=", "").Replace("""", "")
        Dim NEWURL As New Uri(MainURL, Oldurl)
        Dim NewHREF As String = "src=""" & NEWURL.AbsoluteUri & """"
        NewSTR = NewSTR.Replace(OldHREF, NewHREF)
    Next
    Return NewSTR
End Function
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  • 甜味超标
    2020-12-16 04:39

    You should use HtmlAgility pack to load the HTML, access all the hrefs using it, and then use the Uri class to convert from relative to absolute as necessary.

    See for example http://blog.abodit.com/2010/03/a-simple-web-crawler-in-c-using-htmlagilitypack/

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  • 被撕碎了的回忆
    2020-12-16 04:41

    I think url is of type string. Use Uri instead with a base uri pointing to your domain:

    Uri baseUri = new Uri("http://domain.is");
Uri myUri = new Uri(baseUri, url);

System.Net.WebClient client = new System.Net.WebClient();
byte[] dl = client.DownloadData(myUri);
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  • 你的背包
    2020-12-16 04:43

    Simple function

    public string ConvertRelativeUrlToAbsoluteUrl(string relativeUrl)
{

if (Request.IsSecureConnection)
  return string.Format("https://{0}{1}", Request.Url.Host, Page.ResolveUrl(relativeUrl));
else
  return string.Format("http://{0}{1}", Request.Url.Host, Page.ResolveUrl(relativeUrl));

}
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  • 暗喜
    2020-12-16 04:46

    I know this is an older question, but I figured out how to do it with a fairly simple regex. It works well for me. It handles http/https and also root-relative and current directory-relative.

    var host = "http://www.google.com/";
var baseUrl = host + "images/";
var html = "<html><head></head><body><img src=\"/images/srpr/logo3w.png\" /><br /><img src=\"srpr/logo3w.png\" /></body></html>";
var regex = "(?<=(?:href|src)=\")(?!https?://)(?<url>[^\"]+)";
html = Regex.Replace(
    html,
    regex,
    match => match.Groups["url"].Value.StartsWith("/")
        ? host + match.Groups["url"].Value.Substring(1)
        : baseUrl + match.Groups["url"].Value);
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