using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<User> userList = new List<User>();

        userList.Add( new User { Rules = 1, Coupons = "C1", CouponId = 1, Priority = 1,Sum = 0 } );

        userList.Add( new User { Rules = 2, Coupons = "C2", CouponId = 2, Priority = 3,Sum = 0 } );

        userList.Add( new User { Rules = 3, Coupons = "C6", CouponId = 4, Priority = 2,Sum = 0 } );

        userList.Add( new User { Rules = 4, Coupons = "C3", CouponId = 5, Priority = 4,Sum = 0 } );

        userList.Add( new User { Rules = 5, Coupons = "C3", CouponId = 5, Priority = 5,Sum = 0 } );

        userList.Add( new User { Rules = 6, Coupons = "C4", CouponId = 3, Priority = 6,Sum = 0 } );

        userList.Add( new User { Rules = 7, Coupons = "C4", CouponId = 3, Priority = 7,Sum = 0 } );

        userList.Add( new User { Rules = 8, Coupons = "C7", CouponId = 7, Priority = 8,Sum = 0 } );

        userList.Add( new User { Rules = 9, Coupons = "C5", CouponId = 6, Priority = 9,Sum = 0 } );

        userList.Add( new User { Rules = 10, Coupons = "C6", CouponId = 4, Priority = 10 ,Sum = 0 } );

        userList.ForEach(o => o.Sum = userList.Where(k => k.CouponId == o.CouponId).Count());

        userList = userList.OrderByDescending(k => k.Sum).ThenBy(n => n.CouponId).ToList();

        userList.ForEach(k =>

        Console.WriteLine("Rules : " + k.Rules + "   Coupons :  " + k.Coupons + "  CouponId :  " + k.CouponId + "  Priority :  " + k.Priority + "   Sum : " + k.Sum)

        );

    }

}

​

public class User

{

  public int Rules { get; set; }

  public string Coupons { get; set; }

  public int CouponId { get; set; }

  public int Priority { get; set; }

  public int Sum { get; set; }

}