If you know your collection is in ascending order and you want it descending, just reverse it (http://msdn.microsoft.com/en-us/library/b0axc2h2%28v=vs.90%29.aspx). Otherwise you can use the sort method (http://msdn.microsoft.com/en-us/library/3da4abas%28v=vs.90%29.aspx) to sort it, although you might need to create your own comparer. Or you could change your collection to a SortedList (http://msdn.microsoft.com/en-us/library/ms132319%28v=vs.90%29.aspx) so that the list is created in a sorted order.

It might also help to know exactly what type of collection you are using, how you are sorting now that is too slow, and why your collection is composed of single element object arrays instead of strings.