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   1: class Operation

   2: {

   3:     public virtual double operation(int x, int y)

   4:     {

   5:         return x * y;

   6:     }

   7: }

   8: class Addition : Operation

   9: {

  10:     public override double operation(int x, int y)

  11:     {

  12:         return (x + y);

  13:     }

  14: }

  15:  

  16: private void button1_Click(object sender, EventArgs e)

  17: {

  18:     if (comboBox1.SelectedIndex == 0)

  19:     {

  20:         Operation multiplication = new Operation();

  21:         txtResult.Text = multiplication.operation( Convert.ToInt32(txtNum1.Text.Trim()), Convert.ToInt32(txtNum2.Text.Trim() )).ToString();

  22:     }

  23:     else

  24:     {

  25:         Operation addition = new Addition();

  26:         txtResult.Text = addition.operation(Convert.ToInt32(txtNum1.Text.Trim()), Convert.ToInt32(txtNum2.Text.Trim())).ToString();

  27:     }

  28: }

   1: class Operation

   2:    {

   3:        public virtual double operation(int x, int y)  // virtual method可以再重新定義

   4:        {

   5:            return x * y;

   6:        }

   7:    }

   8:    class Multiplication : Operation

   9:    {

  10:  

  11:    }

  12:    class Addition : Operation

  13:    {

  14:        public override double operation(int x, int y)

  15:        {

  16:            return (x + y);

  17:        }

  18:    }

   1: private void button2_Click(object sender, EventArgs e)

   2: {

   3:     Operation[] op = new Operation[2];         // Operation陣列

   4:     op[0] = new Multiplication();              // 存放乘法

   5:     op[1] = new Addition();                    // 存放加法

   6:     MessageBox.Show( "Multiplication: " + op[0].operation( int.Parse(txtNum1.Text), int.Parse(txtNum2.Text)).ToString() );

   7:     MessageBox.Show("Addition: " + op[1].operation(int.Parse(txtNum1.Text), int.Parse(txtNum2.Text)).ToString());

   8: }

   1: Operation[] op = new Operation[2];         // Operation陣列

   2:   op[0] = new Multiplication();              // 存放乘法

   3:   op[1] = new Addition();                    // 存放加法

   4:   int i = comboBox1.SelectedIndex;

   5:   txtResult.Text = op[i].operation(int.Parse(txtNum1.Text), int.Parse(txtNum2.Text)).ToString();