static void Main(string[] args)
        {
            Console.WriteLine("Welcome to Student Management System");
mainprogram:
            Console.Clear();
            Console.WriteLine("Select from the given options :");
            Console.WriteLine("1.Teacher Registration   2.Teacher login  3.Student login");
            int c = Convert.ToInt32(Console.ReadLine());

            try
            {
                switch (c)
                {
                case 1:
                    try
                    {
                        Console.WriteLine("Enter your Name");
                        string p_name = Console.ReadLine();

                        Console.WriteLine("Enter your Password");
                        string p_pass = TurnToStars();
                        if (p_pass.Length < 8)
                        {
                            throw new PassLengthNotValidException("Password should be more than 8 character");
                        }

                        Console.WriteLine("Enter your City");
                        string p_city = Console.ReadLine();
                        Console.WriteLine("Enter your Email");
                        string p_email = Console.ReadLine();
                        Console.WriteLine("Enter your Contact Number");
                        string  p_contact = Console.ReadLine();
                        teacher t1        = new teacher(p_name, p_pass, p_city, p_email, p_contact);
                        t1.selfregistration();
                    }


                    catch (PassLengthNotValidException e)
                    {
                        Console.WriteLine(e.Message);
                    }
                    break;



                case 2:

                    Console.WriteLine("enter user Id and Password to login");
                    int id = int.Parse(Console.ReadLine());
                    Console.WriteLine("enter password");
                    string  pass = TurnToStars();
                    teacher t    = new teacher();

                    int j = t.login(id, pass);
                    if (j == 3)
                    {
                        Console.WriteLine("Logged in successfully!");
                        Console.WriteLine("Enter :");

                        Console.WriteLine("1.To Register new student   2.Update the existing Student    3.Update Your Details    4.Delete Student    5.Delete your ID");
                        int x = int.Parse(Console.ReadLine());
                        if (x == 1)
                        {
                            t.registration();
                        }
                        else if (x == 2)
                        {
                            Console.WriteLine("Enter student ID to edit details");
                            int stid = int.Parse(Console.ReadLine());

                            t.UpdateStudent(stid);
                        }
                        else if (x == 3)
                        {
                            t.Update_teacher(id);
                        }
                        else if (x == 4)
                        {
                            Console.WriteLine("Enter Student ID to delete: ");
                            int did = int.Parse(Console.ReadLine());
                            t.DeleteStudent(did);
                        }
                        else
                        {
                            t.DeleteTeacher(id);
                        }
                    }
                    else
                    {
                        Console.WriteLine("Failed");
                    }
                    break;


                case 3:
                    Console.WriteLine("enter user Id and Password to login");
                    int sid = int.Parse(Console.ReadLine());
                    Console.WriteLine("enter password");
                    string  spass = TurnToStars();
                    student o     = new student();
                    int     i     = o.login(sid, spass);
                    if (i == 1)
                    {
                        Console.WriteLine("Logged in successfully!");
                    }
                    else
                    {
                        Console.WriteLine("Incorrect ID/Password!");
                    }
                    break;
                }
            }
            catch (SqlException e)
            {
                Console.WriteLine(e.Message);
            }

            Console.WriteLine("Press Y to continue or any other key to exit");
            char inp = char.Parse(Console.ReadLine());

            if (inp == 'Y' || inp == 'y')
            {
                goto mainprogram;
            }
        }