using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using Newtonsoft.Json;

​

​

public class Program

{

    public static void Main()

    { 

      Employee.getAllEmployee()

          .GroupJoin(Address.getAllAddress(),

                Employee=>Employee.AddressId,

                Address=>Address.AddressID,

                (Employee,Address)=> new {Employee,Address}

                     )

                .SelectMany(x=>x.Address.DefaultIfEmpty(),

                           ())

    }

}

​

public class Employee {

  public int id {get;set;}

  public string name {get;set;}

  public int AddressId {get;set;}

  public static List<Employee> getAllEmployee(){

    return new List<Employee>(){

      new Employee {id=1,name="e1",AddressId=1},

      new Employee {id=2,name="e2",AddressId=2},

      new Employee {id=3,name="e3",AddressId=1},

      new Employee {id=4,name="e4",AddressId=3},

      new Employee {id=5,name="e5",AddressId=5},

    };

  }

}

​

public class Address{

  public int AddressID {get;set;}

  public string AddresName {get;set;}

 public static List<Address> getAllAddress(){

  return  new List<Address>{

    new Address{AddressID=1,AddresName="address1"},

    new Address{AddressID=3,AddresName="address3"},

    new Address{AddressID=2,AddresName="address2"},

    new Address{AddressID=4,AddresName="address4"}

  };

 }

}