计算器（只实现两个数运算）

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 _125_计算器
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void btnNum0_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum0.Text);
        }
        private void btnNum1_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum1.Text);
        }
        private void btnNum2_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum2.Text);
        }
        private void btnNum3_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum3.Text);
        }
        private void btnNum4_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum4.Text);
        }
        private void btnNum5_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum5.Text);
        }
        private void btnNum6_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum6.Text);
        }
        private void btnNum7_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum7.Text);
        }
        private void btnNum8_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum8.Text);
        }
        private void btnNum9_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnNum9.Text);
        }
        char Symbol;
        private void btnAdd_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnAdd.Text);
            Symbol = '+';
        }
        private void btnMinus_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnMinus.Text);
            Symbol = '-';
        }
        private void btnMultiply_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnMultiply.Text);
            Symbol = '*';
        }
        private void btnDivide_Click(object sender, EventArgs e)
        {
            txtDisplay.AppendText(btnDivide.Text);
            Symbol = '/';
        }
        private void btnEqual_Click(object sender, EventArgs e)
        {
            double result;
            string input = txtDisplay.Text;
            if (Symbol == '+')
            {
                string[] nums = txtDisplay.Text.Split('+');
                result = Convert.ToDouble(nums[0]) + Convert.ToDouble(nums[1]);
            }
            else if (Symbol == '-')
            {
                string[] nums = txtDisplay.Text.Split('-');
                result = Convert.ToDouble(nums[0]) - Convert.ToDouble(nums[1]);
            }
            else if (Symbol == '*')
            {
                string[] nums = txtDisplay.Text.Split('*');
                result = Convert.ToDouble(nums[0]) * Convert.ToDouble(nums[1]);
            }
            else if (Symbol == '/')
            {
                string[] nums = txtDisplay.Text.Split('/');
                result = Convert.ToDouble(nums[0]) / Convert.ToDouble(nums[1]);
            }
            else
            {
                result = 999999999;
            }
            txtDisplay.Clear();
            txtDisplay.Text = result.ToString();
        }
        private void btnC_Click(object sender, EventArgs e)
        {
            txtDisplay.Clear();
        }
        private void btnBack_Click(object sender, EventArgs e)
        {
            try
            {
                txtDisplay.Text = txtDisplay.Text.Substring(0, txtDisplay.Text.Length - 1);
            }
            catch
            { }
        }
        private void Form1_Load(object sender, EventArgs e)
        {
           // txtDisplay.Text = "0";
        }
    }
}