using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<Property> properties = new List<Property>

            {

                new Property { PID =1, PropertyName = "aaa", Availability = true, Price = 20 },

                new Property { PID =2, PropertyName = "bbb", Availability = false, Price = 10 },

                new Property { PID =3, PropertyName = "ccc", Availability = true, Price = 50 },

                new Property { PID =4, PropertyName = "ddd", Availability = false, Price = 80 },

                new Property { PID =5, PropertyName = "eee", Availability = true, Price = 55 },

                new Property { PID =6, PropertyName = "fff", Availability = false, Price = 70 }

            };

​

            List<Favorite> favorites = new List<Favorite>

            {

                new Favorite { FID =1, PID = 4, UserId = 1001 },

                new Favorite { FID =2, PID = 2, UserId = 1005 },

                new Favorite { FID =3, PID = 5, UserId = 1007 }

            };

​

            var result = from p in properties

                         join f in favorites.Where(x => x.UserId == 1005)

                         on p.PID equals f.PID into r

                         from r1 in r.DefaultIfEmpty()

                         select new

                             {

                                 PID = p.PID,

                                 PropertyName = p.PropertyName,

                                 Availability = p.Availability,

                                 Price = p.Price,

                                 FID = r1 != null ? r1.FID : 0,

                                 UserId = r1 != null ? r1.UserId : 0

                             };

​

            Console.WriteLine("PID\tPropertyName\tAvailability\tPrice\tFID\tUserId");

            foreach (var item in result)

            {

                Console.WriteLine("{0}\t{1}\t{2}\t{3}\t{4}\t{5}", item.PID, item.PropertyName, item.Availability, item.Price, item.FID, item.UserId);

            }

    }

}

​

 public class Property

    {

        public int PID { get; set; }

        public string PropertyName { get; set; }

        public bool Availability { get; set; }

        public decimal Price { get; set; }

    }

​

    public class Favorite

    {

        public int FID { get; set; }

        public int PID { get; set; }

        public int UserId { get; set; }

    }