C# - 四則演算

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace pjCalc
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            cmbList.SelectedIndex = 0;
        }

        private void btnCalc_Click(object sender, EventArgs e)
        {
            int value1;
            int value2;
            try
            {
                value1 = int.Parse(txtInput1.Text);
                value2 = int.Parse(txtInput2.Text);
                switch (cmbList.SelectedIndex)
                {
                    case 0:
                        txtAnswer.Text = (value1 + value2).ToString();
                        break;
                    case 1:
                        txtAnswer.Text = (value1 - value2).ToString();
                        break;
                    case 2:
                        txtAnswer.Text = (value1 * value2).ToString();
                        break;
                    case 3:
                        if (value1 % value2  == 0)
                        {
                            txtAnswer.Text = (value1 / value2).ToString();
                        }
                        else
                        {
                            txtAnswer.Text = (value1 / value2).ToString() + "..." + (value1 % value2).ToString();
                        }

                        break;
                    default:
                        ;
                        break;
                }

            }
            catch (Exception ex)
            {
                MessageBox.Show("数値を入力してください。");
            }

        }
    }
}