namespace improve
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            int op1 = 0;
            int op2 = 0;
            int result = 0;
            try
            {
                op1 = Int32.Parse(textBox1.Text);
            }
            catch (System.FormatException)
            {
                MessageBox.Show("左边输入的不是一个double数");
                return;
            }
            catch (System.OverflowException)
            {
                MessageBox.Show("左边输入的值超出表示范围.");
                return;
            }
            try
            {
                op2 = Int32.Parse(textBox2.Text);
                return;
            }
            catch (System.FormatException)
            {
                MessageBox.Show("右边输入的不是一个double数");
                return;
            }
            catch (System.OverflowException)
            {
                MessageBox.Show("右边输入的值超出表示范围.");
                return;
            }
            try//就是提示这里无法访问
            {
                result = checked(op1 * op2);
            }
            catch (System.OverflowException)
            {
                MessageBox.Show("计算结果值超出Int表示范围.");
                return;
            }
            textBox3.Text = result.ToString();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            textBox1.Text="";
            textBox2.Text = "";
            textBox3.Text = "";
        }
    }
}