请教MVC3中怎么实现时间倒排，多谢各位

请问MVC3中如何实现时间倒排，谢谢各位
var db = new DataClasses1DataContext();
  var str = (from r in db.speak 
  select new speaks
  {
  id = r.id,
  submit_time = r.submit_time,
  content = r.content
  }).ToList<speaks>();
  return View(str);
这是我的代码，我现在想按submit_time倒排序查询，orderby submit_time desc,这样的语句在这里该怎么写，谢谢各位

------解决方案--------------------------------------------------------

C# code

  var db = new DataClasses1DataContext();  var str=db.speak.OrderByDescending(r=>r.submit_time).ToList();   return View(str);