Linq

1.

using (DbAppDataContext db = new DbAppDataContext())
    {
        db.Log = Console.Out;
        //取出student
        var student = db.Students.SingleOrDefault<Student>(s => s.ID == id);
 
        if (student == null)
        {
            Console.WriteLine("student is null");
            return;
        }
 
        db.Students.DeleteOnSubmit(student);
 
        db.SubmitChanges();
    }

2.

var q =

　　from c in db.Customers

　　where c.City == "London"

　　select c;

3.

var q = db.Employees.Select(e => e.HireDate).Max();