DataReader的使用

public List<Student> GetList()
        {
            string sql = "select * from Student";
            using (conn = new SqlConnection(connectionstring))
            {
                conn.Open();
                List<Student> list = new List<Student>();
                SqlCommand cmd = new SqlCommand(sql, conn);
                SqlDataReader sdr = cmd.ExecuteReader();
                while (sdr.Read())
                {
                    Student stu = new Student();
                    stu.ID = Convert.ToInt32(sdr[0]);
                    stu.Name = sdr[1].ToString();
                    stu.Sex = Convert.ToInt32(sdr[2]);
                    stu.Age = Convert.ToInt32(sdr[3]);
                    list.Add(stu);
                }
                return list;
            }
        }