How to get text between nested parentheses?

Question

Reg Expression for Getting Text Between parenthesis ( ), I had tried but i am not getting the RegEx. For this example

Regex.Match(script, @"\((.*?)\)").Value

Example:-

add(mul(a,add(b,c)),d) + e - sub(f,g)

Output =>

1) mul(a,add(b,c)),d

2) f,g

Answer 1

.NET allows recursion in regular expressions. See Balancing Group Definitions

var input = @"add(mul(a,add(b,c)),d) + e - sub(f,g)";

var regex = new Regex(@"
    \(                    # Match (
    (
        [^()]+            # all chars except ()
        | (?<Level>\()    # or if ( then Level += 1
        | (?<-Level>\))   # or if ) then Level -= 1
    )+                    # Repeat (to go from inside to outside)
    (?(Level)(?!))        # zero-width negative lookahead assertion
    \)                    # Match )",
    RegexOptions.IgnorePatternWhitespace);

foreach (Match c in regex.Matches(input))
{
    Console.WriteLine(c.Value.Trim('(', ')'));
}