Rename a bunch of files in a specific directory using a shift to increase or decrease their order. The files need to be in the following format: 00_file.txt

renameFilesWithShift.csx

using System;
using System.IO;

var directory = @"C:\directory\";
var shift = 3;

foreach(var file in Directory.GetFiles(directory)) {
	var fileName = Path.GetFileName(file);

	var currentNumber = Int64.Parse(fileName.Substring(0, 2));
	var newNumber = currentNumber + shift;

	var newNumberAsString = string.Empty;
	if (newNumber < 10) {
		newNumberAsString = "0";
	} 
	newNumberAsString = newNumberAsString + newNumber.ToString();

	File.Move(file, string.Format("{0}{1}{2}", directory, newNumberAsString, fileName.Substring(2)));
}