จับคู่ลูกค้ากับคำสั่งซื้อ

using System;
using System.Linq;
record Customer(int Id, string Name);
record Order(int CustomerId, decimal Total);
class Program
{
    static void Main()
    {
        var customers = new[] { new Customer(1, "Ada"), new Customer(2, "Lin") };
        var orders = new[] { new Order(2, 40m), new Order(1, 25m) };
        var rows = customers.Join(orders, c => c.Id, o => o.CustomerId, (c, o) => $"{c.Name}: {o.Total}");
        Console.WriteLine(string.Join(" | ", rows));
    }
}