C# - Insert Large Amount Of Data Using Linq-to-sql?

I need to insert large amount of data into SqlServer 2008. My project is based on linq-to-sql.

I process csv file with 100.000 rows. Each row is mapped to Order object. Order contains also collection of Category and Code objects. I need to map each row to object in order to validate it.

Then I need to insert all these objects into database.

List<Order> orders = Import("test.csv");
db.Orders.InsertAllOnSubmit(orders);
db.SubmitChanges();
OR
foreach(Order order in orders)
db.Orders.InsertOnSubmit(order);
db.SubmitChanges();

Both ways are slow. Is there any workaround? I may use other approach than l2sql for this task.

I read about SqlBulkCopy class - would it handle inserting child entities as well?