Question

Suppose I have a regex pattern and I want to replace the matches of the pattern with something else. In the current pattern there are two groups that will match and each one is numbered ($1 and $2):

Regex pattern = new Regex(@"\[([a-zA-Z0-9_\-]+)\^=([^\]]+)\]");
string replacement = "[starts-with(@$1,$2)]";

Example CSS Selector:

[id^="blah"]

Expected output:

[start-swith(@ID,"blah")] // Note ID is capitalized

Here is another regex pattern:

Regex pattern = new Regex(@"\[([a-zA-Z0-9_\-]+)\*=([^\]]+)\]");
string replacement = "[contains(@$1,$2)]");

When I’m performing the replace, is there any way to capitalize the matches in group $1?

Note: I have numerous patterns that get added to a list and they’re paired with their replacement string, so I have to make the solution works for all of the replacements which require capitalization of some of the matching groups.

Update

I think I just thought of a possible solution: convert the replacement string to a MatchEvaluator and return the capitalized group matches when needed. I think this might work:

Regex pattern = new Regex(@"\[([a-zA-Z0-9_\-]+)\^=([^\]]+)\]");
MatchEvaluator evaluator = new MatchEvaluator((Match m) =>
    {
        return string.Format("[starts-with(@{0},{1})]", m.Groups[1].Value.ToUpper(), m.Groups[2].Value);
    });

If anybody can think of a better solution, then please let me know. Greatly appreciated!

Answer 1

MatchEvaluator is fine, think you burned me 😉 Anyway :

var pattern = @"([a-z]+) ([a-z]+)";
var format = "[starts-with({0}{1}]";

var input = "bla bla";
var result = ReplacePattern(input, pattern, format);

public static string ReplacePattern(string input, string pattern, string format)
{
   if (Regex.Match(input, pattern).Groups.Count != 3) return input;//or throw, or...
   return Regex.Replace(input, pattern, x =>
            string.Format(format,
                          x.Groups[1].Value.ToUpper(), 
                          x.Groups[2].Value));
}