Databases :: Delete Record From Table With Proper Mapping From Linq To Sql?

I am trying to delete record from table with proper mapping from linq to sql.There is an error stating that Rmove method not found and are u missing an assembly reference.

AdventureWorks db = new AdventureWorks("Integrated Security=sspi");
var query = from con in db.Contact
where con.LastName == "Klein"
select con;
foreach (Contact del in query)
{
db.Contact.Remove(del);//???Remove not working
}
db.SubmitChanges();
textBox1.Text = "Contact deleted.";