How do I check if a string contains "(1)" and if it does, increase the number by 1?

Question

If a any given string, at the end contains "(" followed by a number, + ")", i want to increase that value by one. If not Ill just add a "(1)".

Ive tried with something like string.Contains(), but since the value within () can be diffrent i don't know how to always search like this and get the number.

Answer 1

To find a parentheses enclosed number at the end of a string, and increase b 1, try this:

Regex.Replace(yourString, @"(?<=\()\d+(?=\)$)", match => (int.Parse(match.Value) + 1).ToString());

Explanation:

(?<=\\() is a positive look-behind, which matches an open bracket, but does not include it in the match result.

\\d+ matches one or more digits.

(?=\\)$) is a positive look-ahead, which matches a closing bracket at the end of the string.

To add a number if none is present, test the match first:

string yourString = "A string with no number at the end";
string pattern = @"(?<=\()\d+(?=\)$)";
if (Regex.IsMatch(yourString, pattern))
{
    yourString = Regex.Replace(yourString, pattern, match => (int.Parse(match.Value) + 1).ToString());
}
else
{
    yourString += " (1)";
}

Answer 2

You can try regular expressions : Match and Replace the desired fragment, eg

  using System.Text.RegularExpressions;

  ...

  string[] tests = new string[] {
    "abc",
    "def (123)",
    "pqr (123) def",
    "abs (789) (123)",
  };

  Func<string, string> solution = (line) =>
    Regex.Replace(line, 
      @"\((?<value>[0-9]+)\)$", 
      m => $"({int.Parse(m.Groups["value"].Value) + 1})");

  string demo = string.Join(Environment.NewLine, tests
    .Select(test => $"{test,-20} => {solution(test)}"));

  Console.Write(demo);

Outcome:

abc                  => abc              # no numbers
def (123)            => def (124)        # 123 turned into 124
pqr (123) def        => pqr (123) def    # 123 is not at the end of string
abs (789) (123)      => abs (789) (124)  # 123 turned into 124, 789 spared

If we put

  Func<string, string> solution = (line) => {
    Match m = Regex.Match(line, @"\((?<value>[0-9]+)\)$");

    return m.Success
      ? line.Substring(0, m.Index) + $"({int.Parse(m.Groups["value"].Value) + 1})"
      : line + " (1)";
  };

Edit: If we want to put (1) if we haven't any match we can try Match and replace matched text:

abc                  => abc (1)
def (123)            => def (124)
pqr (123) def        => pqr (123) def (1)
abs (789) (123)      => abs (789) (124)

Answer 3

string s = "sampleText";
string pattern = "[(]([0-9]*?)[)]$";

for (int i = 0; i < 5; i++)
{
    var m = Regex.Match(s, pattern);
    if (m.Success)
    {
        int value = int.Parse(m.Groups[1].Value);
        s = Regex.Replace(s, pattern, $"({++value})");
    }
    else
    {
        s += "(1)";
    }

    Console.WriteLine(s);
}

Answer 4

If I understand correctly you have strings such as :

string s1 = "foo(12)"
string s2 = "bar(21)"
string s3 = "foobar" 

And you want to obtain the following:

IncrementStringId(s1) == "foo(13)" 
IncrementStringId(s2) == "bar(22)" 
IncrementStringId(s3) == "foobar(1)"

you could accomplish this by using the following method

public string IncrementStringId(string input)
{
    // The RexEx pattern is looking at the very end of the string for any number encased in paranthesis
    string pattern = @"\(\d*\)$";
    Regex regex = new Regex(pattern);
    Match match = regex.Match(input);
    if (match.Success)
        if (int.TryParse(match.Value.Replace(@"(", "").Replace(@")", ""), out int index))
            //if pattern in found parse the number detected and increment it by 1
            return Regex.Replace(input, pattern, "(" + ++index + ")");
    // In case the pattern is not detected add a (1) to the end of the string
    return input + "(1)";
}

Please make sure you are using System.Text.RegularExpressions namespace that includes Regex class.