private void button1_Click(object sender, RoutedEventArgs e)

        {

            calculate sa = new calculate(int.Parse(textBox1.Text),int.Parse(textBox3.Text),textBox2.Text);

            if (sa.answer == int.Parse(textBox4.Text))

            {

                MessageBox.Show("回答正确");

            }

            else

            {

                MessageBox.Show("回答错误");

            }

 interface chapter

    {

        int answer { get; }

    }

    class calculate:chapter

    {

           private int x1;

        private int x2;

        private string Operator;

        public int result;

        public calculate(int x1, int x2, string Operator)

        {

            this.x1 = x1;

            this.x2 = x2;

            this.Operator = Operator;

        }

        public int answer

        {

            get {

                if (Operator == "+")

                {

                    result = x1 + x2;

                }

                if (Operator == "-")

                {

                    result = x1 - x2;

                }

                if (Operator == "*")

                {

                    result = x1 * x2;

                }

                 if (Operator == "/")

                {

                    result = x1 / x2;

                }

                return result;

            }

        }

    }

}