title: How to find dd/mm/yyyy date on string using c#?
body: <p>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.</p>
  
  <p>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).</p>
  
  <hr>
  
  <p>How can I do that?</p>
  
  <hr>
  
  <p>Code so far:</p>
  
  <pre><code>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 &lt; 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] -&gt; Complete path to the file.");
                      Console.WriteLine("[Addition] -&gt; 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 "";
          }
      }
  }
  </code></pre>