c# 类里面的问题

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

namespace WindowsFormsApplication14
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        int i = 0;
      private void Form1_load(object sender, EventArgs e)
      {
            pictureBox1.Image = imageList1.Images[i];

      }
        
        private void button1_Click(object sender, EventArgs e)
        {
            
            i += 1;
            i = i > imageList1.Images.Count - 1 ? 0 : i;
            pictureBox1.Image = imageList1.Images[i];
            
        }

        

    }
}
我总是感觉这里不需要load 方法   可以直接把load方法去掉  直接 像定义变量意义   pictureBox1.Image = imageList1.Images[i];  求一个合理的解释  尽量说的专业点  拓展的说一下。 我这里没想通 - -