C # list of tuples with multiple sortings

Question

I have a three-dimensional array of tuples:

var CountList = new List<Tuple<int, int, int>>();

The required sort numerically increases on the first int, and then numerically decreases on the second int, therefore

5, 4, 7
4, 5, 6
5, 2, 3
3, 5, 2
2, 4, 1
2, 6, 4

becomes

2, 6 ,4
2, 4, 1
3, 5, 2
4, 5, 6
5, 4, 7
5, 2, 3

Is there a way to specify additional search functions for List.Sort (), or do I need to divide the information into separate lists, sort in descending order in each group, and then add individual list items to the "master" list "in the desired ascending order?

Answer 1

You can use LINQ:

CountList = CountList
    .OrderBy(t => t.Item1)
    .ThenByDescending(t => t.Item2)
    .ToList();

A less clear, but possibly more effective way to use it List.Sort:

CountList.Sort(
(t1, t2) =>
{
    int res = t1.Item1.CompareTo(t2.Item1);
    return res != 0 ? res : t2.Item2.CompareTo(t1.Item2);
});

List.Sort sorts the source list instead of creating a new one.

Answer 2

Enumerable.OrderBy Enumerable.ThenByDescending LINQ

var Sorted = CountList.OrderBy(l=>l.Item1)
                      .ThenByDescending(l => l.Item2)
                      .ToList();

Answer 3

you can use

List<Tuple<int, int, int>> Sorted
  = CountList.OrderBy( iTuple => iTuple.Item1 )
             .ThenByDescending( iTuple => iTuple.Item2 )
             .ToList();

or implement a custom mapper to get lexicographical ordering.

Answer 4

Sorting has an overload that takes a comparison parameter.

CountList.Sort((t1, t2) => {
        int c = t1.Item1.CompareTo(t2.Item1);
        if (c != 0) return c;
        c = t1.Item2.CompareTo(t2.Item2);
        return -c;
    }
);