Every now and again, you are doing something and you need a small screwdriver instead of a hammer. I've been working on a lot of repetitive API work where I end up copying a set of files, renaming them, and then editing them. While I should just write a factory to handle these things, in the meantime I wanted to simplify my rename of a batch of files. So I wrote a little console app for batch renaming (download an executable here). The whole of the code is only 60 lines and that's because I wanted to include a help. So, you can cut and paste from here if you want:

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

namespace bRenamer
{
class Program
{
  static void Main(string[] args)
  {
   if (args.GetUpperBound(0) != 2)
   {
    System.Version AppVersion = System.Reflection.Assembly.GetExecutingAssembly().GetName().Version;
    Console.Clear();
    Console.WriteLine("{4}\tVersion: {0}.{1}.{2}.{3}", AppVersion.Major.ToString(), AppVersion.Minor.ToString(),
     AppVersion.Build.ToString(), AppVersion.Revision.ToString(), System.Reflection.Assembly.GetExecutingAssembly().ManifestModule.Name);
    Console.Write("\r\n\r\n{0}", System.Reflection.Assembly.GetExecutingAssembly().ManifestModule.Name);
    Console.Write(" path oldmatch newmatch\r\n");
    Console.Write("where Path is a legitimate file path\r\n");
    Console.Write("OldMatch is a case sensitive text of what you want to replace in the file name\r\n");
    Console.Write("NewMatch is a what you want to use in the file name\r\n\r\n");
    Console.Write(@"{0} c:\test old newandimproved would change a file named thisoldhouse.txt to thisnewandimprovedhouse.txt\r\n", System.Reflection.Assembly.GetExecutingAssembly().ManifestModule.Name);
   }
   else
   {
    string path = args[0];
    string oldMatch = args[1];
    string newMatch = args[2];
    if (Directory.Exists(path))
    {
     foreach (string fileName in Directory.GetFiles(path))
     {
      FileInfo fi = new FileInfo(fileName);
      try
      {
       if (fi.Name.Contains(oldMatch))
       {
        Console.WriteLine("Renaming {0} to {1}", fi.Name, fi.Name.Replace(oldMatch, newMatch));
        File.Move(fi.FullName, (path.EndsWith(@"\") ? path : path + @"\") + fi.Name.Replace(oldMatch, newMatch));
       }
       else
        Console.WriteLine("Skipping {0} ", fi.Name);
      }
      catch { }
     }
    }
    else
    {
     Console.WriteLine("{0} is not a valid directory", path);
    }
    Console.WriteLine("\r\nDone!");
   }
  }
}
}