LINQ Join Query Operator

The Join operator performs an inner join of two sequences based on matching keys extracted from the elements.

public static void JoinSimpleExample()
{
    var customers = new List<Customer>() {
        new Customer {Key = 1, Name = "Gottshall" },
        new Customer {Key = 2, Name = "Valdes" },
        new Customer {Key = 3, Name = "Gauwain" },
        new Customer {Key = 4, Name = "Deane" },
        new Customer {Key = 5, Name = "Zeeman" }
    };

    var orders = new List<Order>() {
        new Order {Key = 1, OrderNumber = "Order 1" },
        new Order {Key = 1, OrderNumber = "Order 2" },
        new Order {Key = 4, OrderNumber = "Order 3" },
        new Order {Key = 4, OrderNumber = "Order 4" },
        new Order {Key = 5, OrderNumber = "Order 5" },
    };

    var q = from c in customers
            join o in orders on c.Key equals o.Key
            select new {c.Name, o.OrderNumber};

    foreach (var i in q) {
       Console.WriteLine("Customer: {0} Order Number: {1}",
            i.Name.PadRight(11, ' '), i.OrderNumber);
    }

   Console.ReadLine();
}

public class Customer
{
    public int Key;
    public string Name;
}

public class Order
{
    public int Key;
    public string OrderNumber;
}