涉及多个GroupJoin的SQL to LINQ

SELECT Orders.OrderID, Customers.CustomerName, Employees.EmployeeName
FROM Orders
LEFT JOIN Customers ON Orders.CustomerID = Customers.CustomerID
LEFT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID

var query = from order in db.Orders
            join customer in db.Customers on order.CustomerID equals customer.CustomerID into customerGroup
            from customer in customerGroup.DefaultIfEmpty()
            join employee in db.Employees on order.EmployeeID equals employee.EmployeeID into employeeGroup
            from employee in employeeGroup.DefaultIfEmpty()
            select new
            {
                order.OrderID,
                CustomerName = customer != null ? customer.CustomerName : null,
                EmployeeName = employee != null ? employee.EmployeeName : null
            };