Set Operators: Intersect : Intersect « LINQ « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. LINQ
3. Intersect

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

    class Customer
    {
        public string ID { get; set; }
        public string City { get; set; }
        public string Country { get; set; }
        public string Region { get; set; }
        public decimal Sales { get; set; }
    }
    class Order
    {
        public string ID { get; set; }
        public decimal Amount { get; set; }
    }
    class Program
    {
        static void Main(string[] args)
        {
            List<Order> orders = new List<Order> {
              new Order { ID="R", Amount=900 },
              new Order { ID="S", Amount=1000 },
              new Order { ID="T", Amount=1100 }
            };
            List<Customer> customers = new List<Customer> {
              new Customer { ID="Q", City="London", Country="UK", Region="Europe", Sales=8000 },
              new Customer { ID="R", City="Beijing", Country="China", Region="Asia", Sales=9000 },
              new Customer { ID="T", City="Lima", Country="Peru", Region="South America", Sales=2002 }
           };

            var customerIDs = from c in customers select c.ID;
            var orderIDs = from o in orders select o.ID;
            var customersWithOrders = customerIDs.Intersect(orderIDs);
            foreach (var item in customersWithOrders){
                Console.Write("{0} ", item);
            }
        }
    }