Linq Sub-Select

Question

How do I write a sub-select in LINQ.

If I have a list of customers and a list of orders I want all the customers that have no orders.

This is my pseudo code

Answer 1

If this is database-backed, try using navigation properties (if you have them defined):

var res = from c in customers
          where !c.Orders.Any()
          select c;

On Northwind, this generates the TSQL:

SELECT /* columns snipped */
FROM [dbo].[Customers] AS [t0]
WHERE NOT (EXISTS(
    SELECT NULL AS [EMPTY]
    FROM [dbo].[Orders] AS [t1]
    WHERE [t1].[CustomerID] = [t0].[CustomerID]
    ))

Which does the job quite well.