using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var list = new List<Model>();

        list.Add(new Model(){id=1,item1=1,item2=2});

        list.Add(new Model(){id=2,item1=1,item2=1});

        list.Add(new Model(){id=3,item1=1,item2=3});

        list.Add(new Model(){id=4,item1=2,item2=2});

        list.Add(new Model(){id=5,item1=2,item2=1});

        list.Add(new Model(){id=6,item1=3,item2=3});

        list = list.OrderBy(x=>x.item1).ThenByDescending(x=>x.item2).ToList();

        foreach(var x in list){

            Console.WriteLine(x.id);

        }

    }

}

​

public class Model{

    public int id;

    public int item1;

    public int item2;

}