What is the Best way to use Database in the project.

public IEnumerable<instructor> GetInstructorsADONET()
{
    var connString = ConfigurationManager.ConnectionStrings["SchoolContext"].ConnectionString;
    List<instructor> instructors = new List<instructor>();
    using (var conn = new SqlConnection(connString))
    {
        conn.Open();

        var cmd = new SqlCommand("SELECT Person.PersonID, Person.LastName, Person.FirstName, Course.Title, Course.Credits " +
            "FROM Course INNER JOIN " +
                  "CourseInstructor ON Course.CourseID = CourseInstructor.CourseID RIGHT OUTER JOIN " +
                  "Person ON CourseInstructor.PersonID = Person.PersonID " +
                  "WHERE (Person.Discriminator = 'Instructor') " +
                  "ORDER BY Person.PersonID", conn);
        var reader = cmd.ExecuteReader();

        int currentPersonID = 0;
        Instructor currentInstructor = null;
        while (reader.Read())
        {
            var personID = Convert.ToInt32(reader["PersonID"]);
            if (personID != currentPersonID)
            {
                currentPersonID = personID;
                if (currentInstructor != null)
                {
                    instructors.Add(currentInstructor);
                }
                currentInstructor = new Instructor();
                currentInstructor.LastName = reader["LastName"].ToString();
                currentInstructor.FirstMidName = reader["FirstName"].ToString();
            }
            if (reader["Title"] != DBNull.Value)
            {
                var course = new Course();
                course.Title = reader["Title"].ToString();
                course.Credits = Convert.ToInt32(reader["Credits"]);
                currentInstructor.Courses.Add(course);
            }
        }
        if (currentInstructor != null)
        {
            instructors.Add(currentInstructor);
        }

        reader.Close();
        cmd.Dispose();
    }
    return instructors;
}</instructor></instructor></instructor>

public IEnumerable<Instructor> GetInstructors()
{
    List<Instructor> instructors;
    using (var db = new SchoolContext())
    {
        instructors = db.Instructors.Include("Courses").ToList();
    }
    return instructors;
}