Sorts the elements of a sequence in descending order by using the values as keys.

// 11, 7, 2, 1
Enumerable.create(1, 7, 11, 2)
          .orderDescending();

With comparer

// 111, 77, 22, 11
Enumerable.create(11, 77, 111, 22)
          .orderDescending('x, y => y - x');