using System.Collections.Generic;
public static void Main()
List<Customer> cust1 = new List<Customer>()
FirstName = "Joe", LastName = "Smith", Age = 18
FirstName = "Fasil", LastName = "Dires", Age = 31
FirstName = "Bob", LastName = "Dires", Age = 31
List<Customer> cust2 = new List<Customer>()
FirstName = "Kerem", LastName = "Erboke", Age = 45
FirstName = "Fasil", LastName = "Dires", Age = 31
var result = cust1.Join(cust2, c => c.LastName, t => t.LastName, (c, t) => c);