Replace HTML tag content using Regex

Question

I want to encrypt the text content of an HTML Document without changing its layout. The content is stored in pairs of tag , like this : < span style...>text_to_get< /span>. My idea is using Regex to retrieve (1) and to replace each text part with the encrypted text (2). I complete step (1) but have trouble at step (2) . Here is the code I'm working on :

private string encryptSpanContent(string text, string passPhrase, string salt, string  hash, int iteration, string initialVector, int keySize)        
{            
        string resultText = text;
        string pattern = "<span style=(?<style>.*?)>(?<content>.*?)</span>";   
        Regex regex = new Regex(pattern);
        MatchCollection matches = regex.Matches(resultText);          
        foreach (Match match in matches)    
        {                
            string replaceWith = "<span style=" + match.Groups["style"] + ">" + AESEncryption.Encrypt(match.Groups["content"].Value, passPhrase, salt, hash, iteration, initialVector, keySize) + "</span>";                
            resultText = regex.Replace(resultText, replaceWith);
        }
        return resultText;
}

Is this the wrong line (that makes all the texts replaced by the last replaceWith value) ?

            resultText = regex.Replace(resultText, replaceWith);

Can anybody help me to fix this ?

Don't parse HTML with regex. http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags — David, Mar 19 '12 at 17:24

score 3 · Answer 1 · answered Mar 19 '12 at 17:18

It's recommended that you use the HTML Agility Pack if you're going to work with HTML, since you might run into issues with regex, especially on nested tags or malformed HTML.

Assuming your HTML is well-formed and you decide to use a regex, you should use the Regex.Replace method that accepts a MatchEvaluator to replace all occurrences.

Try this approach:

string input = @"<div><span style=""color: #000;"">hello, world!</span></div>";
string pattern = @"(?<=<span style=""[^""]+"">)(?<content>.+?)(?=</span>)";
string result = Regex.Replace(input, pattern,
    m => AESEncryption.Encrypt(m.Groups["content"].Value, passPhrase, salt, hash, iteration, initialVector, keySize));

Here I use a lambada expression for the MatchEvaluator and refer to the "content" group as shown above. I also use look-arounds for the span tags to avoid having to include them in the replacement pattern.

Oh, and how can I write these lines in Java ? I found out that regex in Java is "worse" than it is in C# . `String text = Text; String pattern = ".*?)>(?.*?)"; text = Regex.Replace(text, pattern, m => "" + Decrypt(m.Groups["content"].Value, PassPhrase, Salt, Hash, Iterations, InitialVector, KeySize) + ""); return text;` — Minh Nguyen, May 03 '12 at 14:25

score -2 · Answer 2 · edited Aug 17 '12 at 09:32

-2

Here is a simple solution for replacing HTML Tags

string ReplaceBreaks(string value)
{
    return Regex.Replace(value, @"<(.|\n)*?>", string.Empty);
}

edited Aug 17 '12 at 09:32

sloth

99,095
21
171
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answered Aug 17 '12 at 07:07

Hanzala Ali

19

2

While this is a roughly correct way of matching HTML tags, it will not replace each different tag with a specific string, essentially you will collapse all your tags to one type, losing important information. – Superbest Sep 27 '12 at 02:02

Replace HTML tag content using Regex

2 Answers2