using System.Collections.Generic;
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();