private void Login_Button_Click(object sender, RoutedEventArgs e)
        {
            FileReadWrite file = new FileReadWrite();

            if (usernameTB.Text.Trim() == "" && passwordBox.Password == "")
            {
                MessageBox.Show("Please enter Username and Password.");
            }
            else
            {
                if (file.readStudentFromFile(student, usernameTB.Text.Trim(), passwordBox.Password.Trim()))
                {
                    file.ReadDataFromFile(student);
                    homeScreen studentForm = new homeScreen(student);

                    this.Close();
                    studentForm.ShowDialog();
                }
                else
                {
                    MessageBox.Show("Username and password is incorrect.");
                }
            }
        }