เรื่อง LINQ INSERT ข้อมูล ครับ สงสัย เรื่อง ประกาศ ครับ............

Northwnd db = new Northwnd(@"c:\Northwnd.mdf");

// Query for a specific customer. 
var cust =
    (from c in db.Customers
     where c.CustomerID == "ALFKI" 
     select c).First();

// Change the name of the contact.
cust.ContactName = "New Contact";

// Create and add a new Order to the Orders collection.
Order ord = new Order { OrderDate = DateTime.Now };
cust.Orders.Add(ord);

// Delete an existing Order.
Order ord0 = cust.Orders[0];

// Removing it from the table also removes it from the Customer’s list.
db.Orders.DeleteOnSubmit(ord0);

// Ask the DataContext to save all the changes.
db.SubmitChanges();