private void Button_Click(object sender, RoutedEventArgs e)
        {
            bool con = false;

            if (comboBox.SelectedItem.ToString() == "Savings account")
            {
                BankLogic.AddSavingsAccount(MainPage.ChoosenCustomer, AccountNumber.Text);
                con = true;
            }
            else if (comboBox.SelectedItem.ToString() == "Credit account")
            {
                BankLogic.AddCreditAccount(AccountNumber.Text, MainPage.ChoosenCustomer);
                con = true;
            }
            else if (comboBox.SelectedItem.ToString() == "")
            {
                con = false;
            }

            if (con == true)
            {
                var _Frame = Window.Current.Content as Frame;
                _Frame.Navigate(typeof(MainPage));
            }
        }