using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<myClass> myList = new List<myClass>()

        {

            new myClass(){name="Item1",letter="A", number=3 },

            new myClass(){name="Item2",letter="B", number=2 },

            new myClass(){name="Item3",letter="A", number=1 }

        };

​

        var result = myList.OrderBy(x => x.letter).ThenBy(x => x.number).ToList();

        Console.WriteLine("name:{0}", string.Join(",",result.Select(x=>x.name).ToArray()));

        Console.WriteLine("letter:{0}", string.Join(",",result.Select(x=>x.letter).ToArray()));

        Console.WriteLine("number:{0}", string.Join(",",result.Select(x=>x.number).ToArray()));

    }

}

class myClass

{

    public string name { get; set; }

    public string letter { get; set; }

    public int number { get; set; }

}