How do I sort a List given an ordering method or lambda?

Question

If I have a method or lambda to sort a List<T> e.g. using the spaceship operator (From the documentation: x <=> y - results is negative if x < y, zero if x == y, positive if x > y), how can I sort a list using that method?

There is a Sort(Comparison<T>) method on List<T> but the documentation does not explain how to use it.

For instance, suppose I want to sort a list of strings by their lengths, first in ascending order, then in descending order using a method and a lambda:

using System;
using System.Collections.Generic;

namespace test
{
    class Program
    {
        public static int ascendingMethod (String lhs, String rhs)
        {
            return lhs.Length <=> rhs.Length;
        }

        public static void Main()
        {
            function int(String lhs, String rhs) descendingLambda = (lhs, rhs) => 
                    rhs.Length <=> lhs.Length;

            let list = scope List<String>();
            list.Add("2Foobar");
            list.Add("1Fooba");
            list.Add("3Foob");

            //sort using Descending lamdba
            for(let s in list)
            {
                Console.WriteLine(s);
            }

            // sort using Ascending method
            for(let s in list)
            {
                Console.WriteLine(s);
            }
        }
    }
}

Answer 1

You can assign the lambda or bind a Comparison<T> to the method, then use List<T>.Sort(Comparison<T>).

In the String example, it could look like this:

using System;
using System.Collections.Generic;

namespace test
{
    class Program
    {  
        public static int ascendingMethod (String lhs, String rhs)
        {
            return lhs.Length <=> rhs.Length;
        }

        public static void Main()
        {
            Comparison<String> descendingLambdaComparison = scope (lhs, rhs) => 
                    rhs.Length <=> lhs.Length;
            Comparison<String> ascendingMethodComparison = scope => ascendingMethod;

            let list = scope List<String>();
            list.Add("2Foobar");
            list.Add("1Fooba");
            list.Add("3Foob");

            list.Sort(descendingLambdaComparison);
            for(let s in list)
            {
                Console.WriteLine(s);
            }

            list.Sort(ascendingMethodComparison);
            for(let s in list)
            {
                Console.WriteLine(s);
            }
        }
    }
}