c#窗体简易计算器（初级版）

我是一个初学者，从这些简单的开始做起。

把简单的练熟，便是成功了一小步。

下面是代码完整版，可以实现简单的运算。但是有些细节没考虑。

希望大神们帮我指正。

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 简易计算器
{
    public partial class Frm_Main : Form
    {
        int a = 0, b = 0;                     //储存输入数字的整型
        int total=0;                            //用于储存结果
        int m = 1;                               //用于乘法第一项乘以1
        string s;                                  //用来储存输入的每个数
        string d;                                 //用来辨别进行何种运算
        bool c=false;   
        public Frm_Main()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "1";
            textBox1.Text += "1";
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "2";
            textBox1.Text += "2";
        }

        private void button3_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "3";
            textBox1.Text += "3";
        }

        private void button4_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "4";
            textBox1.Text += "4";
        }

        private void button5_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "5";
            textBox1.Text += "5";

        }

        private void button6_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "6";
            textBox1.Text += "6";
        }

        private void button7_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "7";
            textBox1.Text += "7";
        }

        private void button8_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "8";
            textBox1.Text += "8";
        }

        private void button9_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "9";
            textBox1.Text += "9";
        }

        private void button12_Click(object sender, EventArgs e)           //实现加法
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            d = "+";
            a = int.Parse(s);
            total += a;
            textBox1.Text += "+";
            s = "";
        }

        private void button11_Click(object sender, EventArgs e)                //清空
        {
            textBox1.Text = ""; 
            s = "";
            total = 0;
        }

        private void button14_Click(object sender, EventArgs e)                // 实现减法
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            d = "-";
            a = int.Parse(s);
            if (textBox1.Text ==a.ToString())                                                 //判断是不是第一个数
                total = a;
            else
                total -= a;          
            textBox1.Text += "-";
            s = "";
        }

        private void button16_Click(object sender, EventArgs e)                //实现除法
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            d = "/";
            a = int.Parse(s);    
            if (textBox1.Text == a.ToString())                                             //判断是不是第一个数
                total = a;
            else
                total /= a;
            textBox1.Text += "/";
            s = "";
        }

        private void button15_Click(object sender, EventArgs e)                //实现乘法
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            d = "*";
            a = int.Parse(s);
            m*= a;
            total+= m;
            textBox1.Text += "*";
            s = "";
        }
        private void button13_Click(object sender, EventArgs e)                    //输出结果
        {
            switch(d)
            {
                case "+":
                    b = int.Parse(s);
                    total += b;
                    textBox1.Text += "=";
                    textBox1.Text += total.ToString();
                    break;
                case "*":
                    b = int.Parse(s);
                    total *= b;
                    textBox1.Text += "=";
                    textBox1.Text += total.ToString();
                    m = 1;
                    break;
                case "-":
                    b = int.Parse(s);
                    total -= b;
                    textBox1.Text += "=";
                    textBox1.Text += total.ToString();
                    break;
                case "/":
                    b = int.Parse(s);
                    total /= b;
                    textBox1.Text += "=";
                    textBox1.Text += total.ToString();
                    break;
            }          
        }

        private void button10_Click(object sender, EventArgs e)
        {
            if (c == true)
            {
                textBox1.Text = "";
                c = false;
            }
            s += "0";
            textBox1.Text += "0";
        }
    }
}

欢迎指正，以及提出更多建议。谢谢！