private void btnUpdate_Doctor_Click(object sender, RoutedEventArgs e)
        {
            if (docSelected == null)
            {
                return;
            }



            String   firstname = txtFirstName.Text;
            String   lastname  = txtLastName.Text;
            String   username  = txtUsername.Text;
            String   password  = txtPassword.Text;
            String   type      = "doctor";
            int      catid     = int.Parse(cboCategory.SelectedValue.ToString());
            String   phone     = txtPhone.Text;
            DateTime dob       = (DateTime)txtDob.SelectedDate;
            int      salary    = Convert.ToInt32(txtSalary.Text);
            String   gender    = "male";

            if (((radioFemale.IsChecked ?? false) || (radioMale.IsChecked ?? false)) && !string.IsNullOrEmpty(firstname) &&
                !string.IsNullOrEmpty(lastname) && !string.IsNullOrEmpty(username) && !string.IsNullOrEmpty(password) &&
                !string.IsNullOrEmpty(type) && !string.IsNullOrEmpty(phone) && !string.IsNullOrEmpty(txtDob.Text) &&
                !string.IsNullOrEmpty(txtSalary.Text) && !string.IsNullOrEmpty(cboCategory.Text))
            {
                if (radioFemale.IsChecked ?? false)
                {
                    gender = "female";
                }
            }
            else
            {
                MessageBox.Show("Please make sure all attributes are compelted.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
                return;
            }

            if (username != docSelected.employee.user.username && hms.getUser(username) != null)
            {
                MessageBox.Show("Username already exists!", "Warning!", MessageBoxButton.OK, MessageBoxImage.Warning);
                return;
            }

            docSelected.employee.firstname = firstname;
            docSelected.employee.lastname  = lastname;
            docSelected.employee.dob       = dob;
            docSelected.employee.salary    = salary;
            docSelected.employee.phone     = phone;
            docSelected.employee.gender    = gender;

            docSelected.employee.user.username = username;
            docSelected.employee.user.password = password;
            docSelected.employee.user.type     = type;

            docSelected.catid = catid;

            hms.updateDoctor(docSelected);

            MessageBox.Show("Record updated success.", "Success", MessageBoxButton.OK, MessageBoxImage.Information);
            dataGrid_Doctor.Items.Refresh();
            PatientList = hms.getPatientList();
            dataGrid_Patient.Items.Refresh();
        }