private void Save_Btn_Click(object sender, RoutedEventArgs e)
        {
            this.save_btn.IsEnabled = false;
            String   firstname     = firstnametxt.Text;
            String   lastname      = lastnametxt.Text;
            String   username      = usernametxt.Text;
            String   password      = passwordbox.Password;
            String   phone         = cellno.Text;
            String   gender        = "male";
            String   type          = "doctor";
            int      payment       = Convert.ToInt32(paymenttxt.Text);
            String   specializtion = experty.Text;
            DateTime dob           = new DateTime();

            if (datepicker.SelectedDate != null)
            {
                dob = (DateTime)datepicker.SelectedDate;
            }
            if (((radiofemale.IsChecked ?? false) || (radiomale.IsChecked ?? false)) && !string.IsNullOrEmpty(firstname) &&
                !string.IsNullOrEmpty(lastname) && !string.IsNullOrEmpty(username) && !string.IsNullOrEmpty(password) &&
                !string.IsNullOrEmpty(phone) && !string.IsNullOrEmpty(datepicker.Text) &&
                !string.IsNullOrEmpty(paymenttxt.Text) && !string.IsNullOrEmpty(experty.Text))
            {
                if (radiofemale.IsChecked ?? false)
                {
                    gender = "female";
                }
            }
            else
            {
                MessageBox.Show("Please make sure all attributes are completed.", "Reminder", MessageBoxButton.OK, MessageBoxImage.Warning);
                this.save_btn.IsEnabled = true;
                return;
            }
            if (hmsfac.getUser(username) != null)
            {
                MessageBox.Show("Username already exists!", "Warning!", MessageBoxButton.OK, MessageBoxImage.Warning);
                return;
            }
            User u = new User();

            u.user_name     = username;
            u.user_password = password;
            u.user_type     = type;

            Employee emp = new Employee();

            emp.emp_firstname = firstname;
            emp.emp_lastname  = lastname;
            emp.emp_phone     = phone;
            emp.emp_salary    = payment;
            emp.emp_dob       = dob;
            emp.emp_gender    = gender;
            emp.User          = u;

            Category cat = new Category();

            cat.cat_name = specializtion;

            Doctor doc = new Doctor();

            doc.Employee = emp;
            doc.Category = cat;

            doctorlist.Add(hmsfac.addDoctor(doc));

            firstnametxt.Text       = "";
            lastnametxt.Text        = "";
            usernametxt.Text        = "";
            passwordbox.Password    = "";
            cellno.Text             = "";
            radiomale.IsChecked     = true;
            paymenttxt.Text         = "";
            experty.Text            = "";
            datepicker.Text         = "";
            this.save_btn.IsEnabled = true;
        }