Use LINQ to Create Music Playlists

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

namespace AllM3u
{
    class Program
    {
        const string WINDOWTITLE = "AllM3u Creater v0.1";
        const string A3EXT = ".m3u";
        const string MPEXT = ".mp3";
        const string ALLM3U = "!all" + A3EXT;

        static Guid _folderGuid;
        static Guid _fileGuid;

        static FolderData _ds;

        static void Main(string[] args)
        {
            Console.WriteLine("{0}", WINDOWTITLE);

            // Current folder name
            DirectoryInfo di = new DirectoryInfo(".");
            string workingFolder = di.FullName;

            // Put the dataset into memory
            _ds = new FolderData();

            // Collect files data
            Console.WriteLine("Collecting files information...");
            RecursePath(workingFolder);

            Console.WriteLine("Writing m3u files...");

            // Loop through folders
            foreach (var dr in _ds.dbFolders.Where(x => x.HasMp3s == true))
            {
                Console.Write(".");
                using (StreamWriter sr = new StreamWriter(Path.Combine(dr.Path, ALLM3U)))
                {
                    var resSet = from d in _ds.dbFolders
                                 join f in _ds.dbFiles on d.FolderId equals f.FolderId
                                 where d.Path.StartsWith(dr.Path) && d.HasMp3s == true
                                 select new { FullPath = Path.Combine(d.Path, f.Filename) };
                    foreach (var item in resSet)
                    {
                        sr.WriteLine(item.FullPath.Replace(dr.Path + @"\", ""));
                    }
                }
            }
            Console.WriteLine("Done!");
        }

        private static void RecursePath(string inPath)
        {
            DirectoryInfo folder = new DirectoryInfo(inPath);
            DirectoryInfo[] childFolders = folder.GetDirectories();
            FileInfo[] files = folder.GetFiles();

            bool hasMp3s = false;
            _folderGuid = Guid.NewGuid();

            FolderData.dbFoldersRow fdr = _ds.dbFolders.NewdbFoldersRow();
            fdr.FolderId = _folderGuid;
            fdr.Path = inPath;
            fdr.HasMp3s = hasMp3s;
            _ds.dbFolders.Rows.Add(fdr);

            foreach (var file in files)
            {
                // Does folder contain any mp3s?
                if (!hasMp3s && file.Extension.ToLower().Equals(MPEXT.ToLower()))
                {
                    hasMp3s = true;
                }

                // Remove any existing .m3u playlists
                if (file.Extension.ToLower().Equals(A3EXT.ToLower()))
                {
                    try
                    {
                        file.Delete();
                    }
                    catch (Exception Ex)
                    {
                        Console.WriteLine(string.Format("Can't delete file {0}:\r\n\t{1}", file.FullName, Ex.Message));
                    }
                }

                if (file.Extension.ToLower().Equals(MPEXT.ToLower()))
                {
                    _fileGuid = Guid.NewGuid();

                    FolderData.dbFilesRow rdr = _ds.dbFiles.NewdbFilesRow();
                    rdr.FileId = _fileGuid;
                    rdr.FolderId = _folderGuid;
                    rdr.Filename = file.Name;
                    _ds.dbFiles.Rows.Add(rdr);
                }
            }

            FolderData.dbFoldersRow dr = _ds.dbFolders.Single(x => x.FolderId == _folderGuid);
            dr.HasMp3s = hasMp3s;

            foreach (var item in childFolders)
            {
                RecursePath(Path.Combine(inPath, item.Name));
            }
        }

    }
}