private void equalsButton_Click(object sender, RoutedEventArgs e)
        {
            part2 = Convert.ToDouble(ScreenText.Text);
            ScreenText.Clear();
            switch (select)
            {
            case '+':
                answer          = part1 + part2;
                ScreenText.Text = "" + answer;
                break;

            case '-':
                answer          = part1 - part2;
                ScreenText.Text = "" + answer;
                break;

            case '/':
                answer          = part1 / part2;
                ScreenText.Text = "" + answer;
                break;

            case '*':
                answer          = part1 * part2;
                ScreenText.Text = "" + answer;
                break;
            }
        }
 private void plusButton_Click(object sender, RoutedEventArgs e)
 {
     part1  = Convert.ToDouble(ScreenText.Text);
     select = '+';
     ScreenText.Clear();
 }
 private void clearButton_Click(object sender, RoutedEventArgs e)
 {
     ScreenText.Clear();
 }