using System;

using System.IO;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var extensions = new [] { ".xls", ".htm" };

        var suffixes = new [] { string.Empty, "x", "l" };

        var filename = "foobar";

        var dir = Guid.NewGuid().ToString();

        Directory.CreateDirectory(dir);

        foreach (var extension in extensions) {

            foreach (var suffix in suffixes) {

                var path = Path.Combine(dir, Path.ChangeExtension(filename, extension + suffix));

                File.WriteAllText(path, path);

            }       

        }

        Console.WriteLine("**** ALL FILES ****");

        var allFiles = Directory.EnumerateFiles(dir).ToList();

        foreach (var file in allFiles) Console.WriteLine(file);

        foreach (var extension in extensions) {

            var wildcard = "*" + extension;

            Console.WriteLine();

            Console.WriteLine("**** WILDCARD '{0}' ****", wildcard);

            var found = Directory.EnumerateFiles(dir, wildcard).ToList();

            foreach (var file in found) Console.WriteLine(file);

        }

    }

}