Question

I have a file on which I want to replace the dates but I don’t know what dates are on it and I want to do generic code for me to use the same executable for other files.

I put all content of the file in a string and I want to replace all dates with format dd/mm/yyyy (ex: 19/12/2011) with the actual date (20/12/2011).

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How can I do that?

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Code so far:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ReplaceDates
{
    class Program
    {
        static int Main(string[] args)
        {
            string FileIn = retreiveArgument(args, "i");
            int AddDays = Int32.Parse(retreiveArgument(args, "d"));
            string date = (System.DateTime.Now).AddDays(AddDays).ToString("dd/MM/yyyy");

            string content = "", date2replace = "";

            if (File.Exists(FileIn))
            {
                File.Copy(FileIn, FileIn + ".bkp", true);
                try
                {
                    content = File.ReadAllText(FileIn);

                    // here is what I need to do
                }
                catch (Exception)
                {
                    Console.WriteLine("Error replacing dates in " + FileIn + ".");
                    return 0;
                }
                try
                {
                    File.WriteAllText(FileIn, content);
                    Console.WriteLine("Dates replaced in " + FileIn + ".");
                    return 0;
                }
                catch (Exception)
                {
                    Console.WriteLine("Couldn't write the file " + FileIn);
                    return 2;
                }
            }
            else
            {
                Console.WriteLine("File " + FileIn + " does not exist.");
                return 1;
            }
        }



        private static string retreiveArgument(string[] argument, string argumentName)
        {
            for (int i = 0; i < argument.Length; i++)
            {
                if (argument[i].ToLower().Equals("-h") || argument[i].ToLower().Equals("help") || argument[i].ToLower().Equals("-help") || argument[i].Equals("?") || argument[i].Equals("-?"))
                {
                    Console.WriteLine("Usage : ");
                    Console.WriteLine("ReplaceDates.exe -i [Input File] -d [Addition]");
                    Console.WriteLine("[Input File] -> Complete path to the file.");
                    Console.WriteLine("[Addition] -> Adds the specified value in days to the actual date.");
                    Console.WriteLine();
                    Console.WriteLine("This executable replaces the data from the input file.");
                }
                else
                {
                    if (argument[i].Equals("-" + argumentName))
                    {
                        return argument[i + 1].Trim();
                    }
                }
            }
            return "";
        }
    }
}

Answer 1

Here’s a solution using a MatchEvaluator. Tweak the regular expression if desired;

string UpdateDates(string input)
{
    return Regex.Replace(input, @"\d{2}/\d{2}/\d{4}", m => DateTime.Now.ToString("dd/MM/yyyy"));
}