如何在LINQ中进行外连接？

var query = from customer in customers
            join order in orders on customer.CustomerID equals order.CustomerID into gj
            from subOrder in gj.DefaultIfEmpty()
            select new { customer.CustomerName, OrderID = subOrder?.OrderID };

foreach (var result in query)
{
    Console.WriteLine($"Customer: {result.CustomerName}, OrderID: {result.OrderID ?? "No Order"}");
}