using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public class A

{

        public A(float x1, float x2)

        {

            this.x1 = x1;

            this.x2 = x2;

        }

    public float x1;

    public float x2;

}

​

    public static void Main()

    {

        List<A> list = new List<A>();

​

        list.Add(new A(5, 1));

        list.Add(new A(7, 2));

        list.Add(new A(4, 3));

        list.Add(new A(2, 4));

​

        var ordered = list

            .OrderByDescending(x => x.x1)

            .ThenByDescending(x => x.x2);

​

        foreach(var val in ordered)

            Console.WriteLine($"{val.x1} - {val.x2}");  

    }

}