Increment a number within a string (C#)

Question

Hi - I have a string with a number at the end, after a dash ("-"). I'd like to create that same string with that number incremented by 1. Pretty simple, but I'm wondering if there's a better approach to this? Thanks!

string oldString = "BA-0001-3";
int lastIndex = oldString.LastIndexOf("-");
string oldNumber = oldString.SubString(lastIndex + 1);
string oldPartialString = oldString.SubString(0, lastIndex);
int newNumber = Convert.ToInt32(oldNumber) + 1;

string newString = oldPartialString + newNumber.ToString();

Answer 1

Regex?

Example:

Regex.Replace("BA-0001-3", @"[A-Z]{2}-\d{4}-(\d+)", 
    m => (Convert.ToInt32(m.Groups[1].Value) + 1).ToString())

Answer 2

Honestly, I think this approach is right.

Answer 3

I would probably use my friend string.Split:

string oldString = "BA-0001-3";
string[] parts = oldString.Split('-');
parts[parts.Length-1] = (Convert.ToInt32(parts[parts.Length-1])+1).ToString();
string newString = string.Join("-", parts);

A small tweak that will perhaps make it quicker (by accessing parts.Length and subtracting 1 only once - didn't profile so it's purely a guess, and it is likely a marginal difference anyway), but above all more robust (by using int.TryParse):

string oldString = "BA-0001-3";
string[] parts = oldString.Split('-');
int number;
int lastIndex = parts.Length-1;
parts[lastIndex] = (int.TryParse(parts[lastIndex], out number) ? ++number : 1).ToString();
string newString = string.Join("-", parts);

Answer 4

Here's an example of how it could be done with RegEx:

public void Test()
{
    System.Text.RegularExpressions.Regex rx = new Regex(@"(?<prefix>.*\-)(?<digit>\d+)");
    string input = "BA-0001-3";
    string output = string.Empty;

    int digit = 0;
    if (int.TryParse(rx.Replace(input, "${digit}"), out digit))
    {
        output = rx.Replace(input, "${prefix}" + (digit + 1));
    }
    Console.WriteLine(output);
}

Answer 5

Updated per Ahmad Mageed's comments below. This is his answer much more than it is mine now :-)

I would do it the way you have it now, but for fun wanted to see if I could do it with linq.

var x = "BA-0001-3".Split('-');

var y = x.First() + "-" + x.ElementAt(1) + "-" + (Convert.ToInt32(x.Last()) + 1);

This works in LINQPad.

Edit: Obviously I'm not a pro with linq. Hopefully there will be other answers/comments on how this can be improved.

Answer 6

Here is an example of a class that exposes the three parts of your "part number". Not particularly fancy (also note the absence of error checking/validation).

  class Program
  {
    static void Main(string[] args)
    {
      PartNumber p1 = new PartNumber("BA-0001-3");
      for (int i = 0; i < 5; i++)
      {
        p1.Sub++;
        Debug.WriteLine(p1);
      }

      PartNumber p2 = new PartNumber("BA", 2, 3);
      for (int i = 0; i < 5; i++)
      {
        p2.Sub++;
        Debug.WriteLine(p2);
      }

    }
  }

  class PartNumber
  {
    public PartNumber(string make, int model, int sub)
    {
      Make = make;
      Model = model;
      Sub = sub;
    }

    public PartNumber(string part)
    {
      //Might want to validate the string here
      string [] fields = part.Split('-');

      //Are there 3 fields?  Are second and third fields valid ints?
      Make = fields[0];
      Model = Int32.Parse(fields[1]);
      Sub = Int32.Parse(fields[2]);
    }

    public string Make { get; set; }
    public int Model { get; set; }
    public int Sub { get; set; }

    public override string ToString()
    {
      return string.Format("{0}-{1:D4}-{2}", Make, Model, Sub);
    }
  }

Answer 7

Using the regex (which already seems to have now been filled in with more details) I end up with something like:

var regex = new Regex(@"^(?<Category>[A-Za-z]{1,2})-(?<Code>[0-9]{4})-(?<Number>[0-9]+)$");
var newCode = regex.Replace("BA-0001-3", new MatchEvaluator(ReplaceWithIncrementedNumber));

Where the MatchEvaluator function is:

public static string ReplaceWithIncrementedNumber(Match match)
{
    Debug.Assert(match.Success);
    var number = Int32.Parse(match.Groups["Number"].Value);
    return String.Format("{0}-{1}-{2}", match.Groups["Category"].Value, match.Groups["Code"].Value, number + 1);
}