C#怎么用代表和窗体实现简单计算器

我自己写的代码，写不下去了，求救！！

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

namespace sizheyunsuan
{
    public partial class Form1 : Form
    {
        public static  string sun;

        public Form1()
        {
            InitializeComponent();
        }
        public static void Add(double a, double b)
        {

            sun =Convert .ToString( a + b);
        }
        public static void Sub(double a, double b)
        {

            sun =Convert .ToString ( a - b);
        }
        public static void Mul(double a, double b)
        {

            sun =Convert .ToString( a * b);
        }
        public static void Div(double a, double b)
        {

            sun =Convert .ToString( a / b);

        }
        public void button1_Click(object sender, EventArgs e)
        {
            bool  s = true ;
        }

        public delegate void Wo(double a,double b);
        public  void Form1_Load(object sender, EventArgs e)
        {
            double a = Convert.ToDouble(textBox2 .Text );
            double b = Convert.ToDouble(textBox3.Text);
            Form1.Wo first = new Form1.Wo(Add );
            Form1.Wo second = new Form1.Wo(Sub );
            Form1.Wo three = new Form1.Wo(Mul );
            Form1.Wo fure = new Form1.Wo(Div );
            if(s  ==true )
            {
                first(a, b);
                textBox4.Text = sun;
            }
            if (Convert.ToBoolean(button2.Click) == true)
            {
                second (a, b);
                textBox4.Text = sun;
            }
            if (Convert.ToBoolean(button3.Click) == true)
            {
                three (a, b);
                textBox4.Text = sun;
            }
            if (Convert.ToBoolean(button4 .Click ) == true)
            {
                fure (a, b);
                textBox4.Text = sun;
            }
        }




    }

}
C# 代表窗体

补充：.NET技术 ,  C#