If you want to add a record to a table or remove a record from a table, creating or deleting an object in memory is not enough. The DataContext instance must be notified also. This can be
done directly by calling Add or Remove on the corresponding Table collection (these methods
operate on the in-memory copy of the data; a subsequent SubmitChanges call will forward the
SQL commands to the database):

var newCustomer = new Customer {
CustomerID = “DLEAP”,
CompanyName = “DevLeap”,
Country = “Italy” };
db.Customers.Add( newCustomer );
var oldCustomer = db.Customers.Single( c => c.CustomerID == “FRANS” );
db.Customers.Remove( oldCustomer );