static void Main(string[] args) { int temp; string tempstr; ClassCtrl classCtrl = new ClassCtrl(); DBCtrl dbCtrl = new DBCtrl(); DBCon dbCon = new DBCon(); int id = 1; SqlDataReader rs = dbCon.ExecuteStringGet("SELECT * FROM Class where id=(SELECT classId FROM Student where id=" + id + ");"); bool tempb = rs.(); Console.WriteLine(tempb); Console.WriteLine(rs.GetInt32(0)); //for (int i = 0; i<10; i++) // { // temp = dbCtrl.GetClassFromStudentId(i).Id; // Console.WriteLine(temp); // } // for (int i = 0; i<10; i++) // { // temp = classCtrl.GetClassByStudentId(i).Id; // } }