How to use named groups when performing a Regex.Replace()

Question

How do I use named captures when performing Regex.Replace? I have gotten this far and it does what I want but not in the way I want it:

[TestCase("First Second", "Second First")] public void NumberedReplaceTest(string input, string expected) {     Regex regex = new Regex("(?<firstMatch>First) (?<secondMatch>Second)");     Assert.IsTrue(regex.IsMatch(input));     string replace = regex.Replace(input, "$2 $1");     Assert.AreEqual(expected, replace); } 

I want to match the two words with named captures and then use the (named) captures when performing the replace.

Answer 1

Instead of "$2 $1", you can use "${secondMatch} ${firstMatch}".

There is a list of all the replacements you can do here.

Here is an abbreviated list:

$number - The captured group by number.

${name} - The captured group by name.

$$ - $ literal.

$& - Entire match.

$` - The input string before the match.

$' - The input string after the match.

$+ - The last group captured.

$_ - The entire input string.

Answer 2

Simply replace with ${groupName}

[TestCase("First Second", "Second First")] public void NumberedReplaceTest(string input, string expected) {     Regex regex = new Regex("(?<firstMatch>First) (?<secondMatch>Second)");     Assert.IsTrue(regex.IsMatch(input));     string replace = regex.Replace(input, "${secondMatch} ${firstMatch}");     Assert.AreEqual(expected, replace); }