My first code use MonoDevelop edit, for checking error code used situation in a project.

gistfile1.cs

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

namespace CheckUnusedErrorCode
{
  class MainClass
	{
		public static void Main (string[] args)
		{
			var allCodes = GetAllErrorCodes ();

			var fileNames = Directory.GetFiles ("EclipseProjectFolder", "*.java", SearchOption.AllDirectories);

			foreach (var code in allCodes) {
				bool found = false;
				foreach (var fileName in fileNames) {
					int counter = 0;
					string line;

					using (StreamReader sr = new StreamReader(fileName)) {
						while ((line = sr.ReadLine()) != null) {
							if (line.Contains (code)) {
								found = true;
								Console.WriteLine (counter.ToString () + ": " + line);
							}
						
							counter++;
						}
					}
				}

				if (!found) {
					Console.WriteLine (string.Format ("Code: {0} not found!", code));
				}
			}

			Console.Read ();
		}

		private  static List<string> GetAllErrorCodes ()
		{
			XElement root = XElement.Load ("ErrorCodes.xml");

			System.Diagnostics.Debug.Assert (root != null);
			
			var query = from e in root.Elements ()
				select e.Attribute ("Code").Value;

			return query.ToList ();
		}
	}
}