public static void DemoContains() {
nwDataContext db = new nwDataContext(Connections.ConnectionString);
db.Log = Console.Out;

var query =
from c in db.Customers
where !(from o in db.Orders
select o.CustomerID)
.Contains(c.CustomerID)
select new { c.CustomerID, c.CompanyName };

foreach (var c in query) {
	Console.WriteLine(c);
}
}
