Some guy in ##csharp asked for a solution to this...

gistfile1.cs

using System;
using System.Linq;
using System.Collections.Generic;
class Test {
        static void Main()
        {
                var items = new List<string>() {
                "foo_20120212",
                "foo_20120213",
                "foo_20120214",
                "foo_20120215",
                "baz_20120212",
                "baz_20120213",
                "baz_20120214",
                "baz_20120215"};
                
                var v = items.Select(c => new { Date = c.Split('_')[1], Str = c})
                             .Select(g => new { Date = DateTime.ParseExact(g.Date,"yyyyMMdd",CultureInfo.InvariantCulture), Str = g.Str})
                             .OrderByDescending(h => h.Date).ToList();
                
                v.ForEach(x => Console.WriteLine(String.Format("date: {0}, str: {1}",x.date,x.str)));
        }
}

Output:


date: 15/02/2012 12:00:00 AM, str: foo_20120215
date: 15/02/2012 12:00:00 AM, str: baz_20120215
date: 14/02/2012 12:00:00 AM, str: foo_20120214
date: 14/02/2012 12:00:00 AM, str: baz_20120214
date: 13/02/2012 12:00:00 AM, str: foo_20120213
date: 13/02/2012 12:00:00 AM, str: baz_20120213
date: 12/02/2012 12:00:00 AM, str: foo_20120212
date: 12/02/2012 12:00:00 AM, str: baz_20120212