winform制作简单计算器

public Form1()
        {
            InitializeComponent();
            textBox2.Text = "0";//主显示屏
            textBox1.Text = "";//顶端副显示屏
            textBox3.Text = "";//中间变量，隐藏
            
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
        //数字按键
        private void button21_Click(object sender, EventArgs e)
        {
            if (sender is Button)
            {
                Button btn = sender as Button;
                if (textBox2.Text == "0")//如果主屏幕为0
                {
                    textBox2.Text = btn.Text;//输入几就显示几
                }
                else
                {
                    if (yunsuanfu)//上个按键是运算符
                    {
                        textBox2.Text = btn.Text;//主屏幕只显示本次输入的数字
                        yunsuanfu = false;
                    }
                    else
                    {
                        textBox2.Text += btn.Text;//上个按键不是运算符，主屏幕右侧累添上这个数字
                    }
                }
            }
        }

        //加减乘除
        private bool yunsuanfu = false;
        private double jieguo1 = 0;//点击加减乘除运算符显示的结果
        private string text = "";
        private void button26_Click(object sender, EventArgs e)
        {
            if (sender is Button)
            {
                Button btn = sender as Button;
                text = btn.Text;
                if(textBox3.Text=="")
                {
                    textBox3.Text = btn.Text;
                }
                //判断上一步点击的是否是运算符
                if (yunsuanfu==false)//不是运算符
                {
                    textBox1.Text += textBox2.Text + text;
                    yunsuanfu = true;
                    if(textBox3.Text=="+")
                    {
                        jieguo1 += Convert.ToDouble(textBox2.Text);
                        textBox2.Text = jieguo1.ToString();
                    }
                    else if (textBox3.Text == "-")
                    {
                        jieguo1 -= Convert.ToDouble(textBox2.Text);
                        textBox2.Text = jieguo1.ToString();
                    }
                    else if (textBox3.Text == "*")
                    {
                        if (jieguo1 != 0)
                        {
                            jieguo1 = jieguo1 * Convert.ToDouble(textBox2.Text);
                        }
                        else
                        {
                            jieguo1 = Convert.ToDouble(textBox2.Text);
                        }
                        textBox2.Text = jieguo1.ToString();
                    }
                    else if (textBox3.Text == "/")
                    {
                        if (Convert.ToDouble(textBox2.Text) != 0)
                        {
                            if (jieguo1 != 0)
                            {
                                jieguo1 = jieguo1 / Convert.ToDouble(textBox2.Text);
                            }
                            else
                            {
                                jieguo1 = Convert.ToDouble(textBox2.Text); ;
                            }
                            textBox2.Text = jieguo1.ToString();
                        }
                        else
                        {
                            textBox2.Text = "除数不能为0";
                        }
                    }
                    
                    textBox3.Text = text;
                }
                else
                {
                    if (textBox1.Text.Length > 0)
                    {
                        textBox1.Text = textBox1.Text.Substring(0, textBox1.Text.Length - 1) + text;
                        textBox3.Text = text;
                    }
                    else
                    {
                        textBox3.Text = text;
                    }
                    yunsuanfu = false;
                }
            }
        }

        //小数点
        private void button25_Click(object sender, EventArgs e)
        {
            //判断上一步点击的是否是运算符
            if (yunsuanfu == false)//不是运算符
            {
                if (textBox2.Text.Contains(".") == false)
                {
                    textBox2.Text = textBox2.Text + ".";
                }
            }
            else
            {
                textBox2.Text = "0.";
                yunsuanfu = false;
            }
        }

        //等号
        private double jieguo = 0;
        private string text4 = "";
        private string text5 = "";
        private void button28_Click(object sender, EventArgs e)
        {
            jieguo = jieguo1;
            jieguo1 = 0;
            text4 = textBox3.Text;
            textBox3.Text = "";
            text = "";
            if (text4 == "")
            {
                text4 = button28.Text;
            }

            textBox1.Clear();
            textBox1.Text = "";
            //判断上一步点击的是否是运算符
            if (yunsuanfu == false)//不是运算符
            {
                yunsuanfu = true;
                if (text4 == "+")
                {
                    jieguo += Convert.ToDouble(textBox2.Text);
                    textBox2.Text = jieguo.ToString();
                }
                else if (text4 == "-")
                {
                    jieguo -= Convert.ToDouble(textBox2.Text);
                    textBox2.Text = jieguo.ToString();
                }
                else if (text4 == "*")
                {
                    if (jieguo != 0)
                    {
                        jieguo = jieguo * Convert.ToDouble(textBox2.Text);
                    }
                    else
                    {
                        jieguo = Convert.ToDouble(textBox2.Text);
                    }
                    textBox2.Text = jieguo.ToString();
                }
                else if (text4 == "/")
                {
                    if (textBox2.Text != "0")
                    {
                        if (jieguo != 0)
                        {
                            jieguo = jieguo / Convert.ToDouble(textBox2.Text);
                        }
                        else
                        {
                            jieguo = Convert.ToDouble(textBox2.Text); ;
                        }
                        textBox2.Text = jieguo.ToString();
                    }
                    else
                    {
                        textBox2.Text = "除数不能为0";
                    }
                }
                else if (text4 == "=")
                {
                    jieguo = jieguo;
                }
                
                text5 = text4;
                text4 = button28.Text;
            }
            else
            {
                yunsuanfu = false;
                double jishu = 0;
                if (text4 == "+")
                {
                    jishu = jieguo;
                    jieguo += jishu;
                    
                    textBox2.Text = jieguo.ToString();
                }
                else if (text4 == "-")
                {
                    jishu = jieguo;
                    jieguo -=jishu;
                    
                    textBox2.Text = jieguo.ToString();
                }
                else if (text4 == "*")
                {
                    jishu = jieguo;
                    jieguo=jieguo*jishu;
                    
                    textBox2.Text = jieguo.ToString();
                }
                else if (text4 == "/")
                {
                    if (jieguo != 0)
                    {
                        jishu = jieguo;
                        jieguo = jieguo / jishu;
                        
                        textBox2.Text = jieguo.ToString();
                    }
                    else
                    {
                        textBox2.Text = "除数不能为0";
                    }
                }
                else if (text4 == "=")
                {
                    jishu =Convert.ToDouble(textBox1.Text);
                    if (text5 == "+")
                    {
                        jieguo+=jishu ;
                    }
                    else if (text5 == "-")
                    {
                        jieguo-=jishu;
                    }
                    else if (text5 == "*")
                    {
                        jieguo *=jishu;
                    }
                    else if (text5 == "/")
                    {
                        if (jishu != 0)
                        {
                            jieguo /= jishu;
                        }
                        else
                        {
                            textBox2.Text = "除数不能为0";
                        }
                    }
                }
            }
            yunsuanfu = false;
            
        }
        //按键C
        private void button8_Click(object sender, EventArgs e)
        {
            textBox2.Clear();
            textBox1.Clear();
            textBox3.Clear();
            textBox2.Text = "0";
            textBox1.Text = "";
            textBox3.Text = "";
            jieguo = 0;
            jieguo1 = 0;
            yunsuanfu = false;
            text = "";
            text4 = "";
            text5 = "";
        }
        //CE键
        private void button7_Click(object sender, EventArgs e)
        {

            textBox2.Clear();
            textBox2.Text = "0";
        }
        //退格键
        private void button6_Click(object sender, EventArgs e)
        {
            if (textBox2.Text.Length > 1)
            {
                textBox2.Text = textBox2.Text.Substring(0, textBox2.Text.Length - 1);
            }
            else if (textBox2.Text.Length == 1)
            {
                textBox2.Text = textBox2.Text.Substring(0, textBox2.Text.Length - 1);
                textBox2.Text = "0";
            }
            else
            {
                textBox2.Text = "0";
            }
        }
        //主屏幕字体随个数变化而变化
        private void textBox2_TextChanged(object sender, EventArgs e)
        {
            if (textBox2.Text.Length < 8)
            {
                this.textBox2.Font = new System.Drawing.Font("宋体", 21.75f);
            }
            if (textBox2.Text.Length > 8)
            {
                this.textBox2.Font = new System.Drawing.Font("宋体", 15f);
            }
            if (textBox2.Text.Length > 12)
            {
                this.textBox2.Font = new System.Drawing.Font("宋体", 13f);
            }
            if (textBox2.Text.Length > 16)
            {
                this.textBox2.Font = new System.Drawing.Font("宋体", 11f);
            }
        }