C#代码中出现的小问题，小白求指教

Question

  private void equal_Click(object sender, EventArgs e)
        {
            int num1 = int.Parse(txtNum1.Text.Trim());
            int num2 = Convert.ToInt32(txtNum2.Text.Trim());
            switch (cboCaoZuoFu.Text.Trim())
            {
                case"+":
                result.Text=(num1 + num2).ToString ;
                break;
                case"-":
                result.Text = (num1 - num2).ToString;
                break;
                case"*":
                result.Text = (num1 * num2).ToString;
                break;
                case"/":
                result.Text = (num1 / num2).ToString;
                break;
                defaut:
                result.Text = "未知结果！";
                break;
            }

Answer 1

(num1 + num2).ToString记得在后面加上括号，(num1 + num2).ToString()