How would that regular expression be?

Question

I have an expression that follows some rules:

• The character ' must be first and last character
• There can be zero-or-more spaces inside ''
• There can be zero-or-more % inside ''
• There can be zero-or-more words (letters and numbers) inside ''

Expression:

(?i)^(?<q>['])[%\p{Zs}\p{L}\p{N}|()]*\k<q>$

Now I need another expression to replace all ) and ( in a string for "TEST" for example, but only when they are not surrounded by ''. The trick is that when ) or ( are surrounded by '' but these characters belong to a different pair of '', it should not pass.

Example of results:

    '(' > pass
    ' ( ' > pass
    ')'   > pass
    ' ) '   > pass
    ' content here ' ' )'  > pass
    ' content here' ) ' another content'  > does not pass

Note that the first content has its '', and the second as well. Any ) or ( should not pass if its in between them.

I'm not a pro with regular expressions, so if you don't know how it would be, any documentation or tutorial related would be of great help.

Answer 1

I think this should do it:

Regex regex = new Regex(@"^'[^']*?'(?:(?:[^()]*)'[^']*?')*$");

Edit Demo

class Program
{
    static void Main(string[] args)
    {
        Regex regex = new Regex(@"^'[^']*?'(?:(?:[^()]*)'[^']*?')*$");

        string shouldPass1 = "'('";
        string shouldPass2 = "' ( '";
        string shouldPass3 = "')'";
        string shouldPass4 = "'('";
        string shouldPass5 = "' content here ' ' )'";
        string shouldFail = "' content here' ) ' another content'";

        Console.WriteLine("Pass1 : {0}",regex.IsMatch(shouldPass1));
        Console.WriteLine("Pass2 : {0}", regex.IsMatch(shouldPass2));
        Console.WriteLine("Pass3 : {0}", regex.IsMatch(shouldPass3));
        Console.WriteLine("Pass4 : {0}", regex.IsMatch(shouldPass4));
        Console.WriteLine("Pass5 : {0}", regex.IsMatch(shouldPass5));
        Console.WriteLine("Fail : {0}", regex.IsMatch(shouldFail));

        string wholeThing = string.Format(
            "{0}\n{1}\n{2}\n{3}\n{4}\n{5}",
            shouldPass1,
            shouldPass2,
            shouldPass3,
            shouldPass4,
            shouldPass5,
            shouldFail);

        Console.WriteLine("Alltogether (should fail too): {0}", regex.IsMatch(wholeThing));
    }
}

Or without Regex (Tim Schmelter would be proud of me):

private static bool IsMatch(string text)
{
    bool result = text[0] == '\'' && text[text.Length - 1] == '\'';
    bool opened = false;

    for (int i = 0; result && i < text.Length; i++)
    {
        char currentchar = text[i];

        if (currentchar == '\'')
        {
            opened = !opened;
        }
        if (!opened && (currentchar == '(' || currentchar == ')'))
        {
            result = false;
        }
    }

    return result;
}