Question

Hi I am trying to use the solution from

Find all pattern indexes in string in C#

However, it doesn’t work in my situation

string sentence = "A || ((B && C) || E && F ) && D || G";
string pattern = "(";
IList<int> indeces = new List<int>();
foreach (Match match in Regex.Matches(sentence, pattern))
{
  indeces.Add(match.Index);
}

It produces error , “parsing “(” – Not enough )’s”.

I am not sure what I have done wrong here.

Appreciate any help.

Thanks,

Balan Sinniah

Answer 1

I am not sure what I have done wrong here.

You’ve forgotten that ( has a special meaning within regular expressions. If you use

string pattern = @"\(";

it should work, I believe. Alternatively, just keep using string.IndexOf given that you’re not really using the pattern-matching of regular expressions.

If you are going to use regular expressions, I’d personally create a Regex object rather than using the static method:

Regex pattern = new Regex(Regex.Escape("("));
foreach (Match match in pattern.Matches(sentence))
...

That way there’s rather less scope for confusion around which argument is the input text and which is the pattern.