Zamiana na LINQ ?

Jak ten kodzik zamienic na postac w LINQ ?

update[Person] set [FirstName]=@FirstName,
            [LastName]=@LastName
            where [PersonID]=@PersonID 

var person = (from p in db.Person where p.PersonID==123 select p).Single();
person.FirstName = "Anna";
person.LastName = "Kowalska";
db.SubmitChanges();

var item = db.Persons.Single(x=>x.Id == 123);
item.FirstName = "Jan";
item.SecondName = "Kowalski";
db.SaveChanges();