regexp: how to extract substring

Question

I have two strings: "word1|word2" , "word2|word1"

Is there any way with regexp to extract word2 from these strings if it contains word1 ?

Answer 1

split the string by | into array and then find any string you like to find

Answer 2

I believe something like this would do it:

  var input = new String[] { "word1|word2", "word2|word1" };
  var regexp = @"word1\|(?<GROUP>.*)|(?<GROUP>.*)\|word1";
  foreach (var word in input)
  {
    var match = Regex.Match(word, regexp, RegexOptions.IgnoreCase);
    Console.WriteLine(match.Groups["GROUP"].Value);
  }

But your requirements are quite unclear to me, so please feel free to ellaborate :-)

Answer 3

I would go for a more flexible approach like splitting on the "|" and checking each part, and saving the other one if you find a match.

If you really need to use regex, something like (word1\\|(.*)|(.*)\\|word1) would put word2 into backreference 1.

You may need to tweak the (.*) part, depending on whether this string is by itself or embedded in other text that should not be matched.

Answer 4

Or use a look around...

 (?<=^word1\|).*|.*(?=\|word1$)

That way you can use

 match.Value

And disregard Groups and Captures altogether.