在 Form1_Load中能否对控件进行绘图？

我尝试在pictureBox控件上绘图，下面是代码：

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 WindowsFormsApp2
{
    public partial class Form1 : Form
    {
        private int x;       //工人当前位置(x,y)
        private int y;
        public Rectangle myRectangle; //自己
        public Graphics gr; //PicShow的Graphics对象

        public Form1()
        {
            InitializeComponent();
        }

        private void drawimage()
        {
            myRectangle = new Rectangle(x, y, 80, 30);
            gr = pictureBox1.CreateGraphics();
            myRectangle.Show(gr);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            x = 10;
            y = 370;
            myRectangle = new Rectangle(x, y, 80, 30);
            gr = pictureBox1.CreateGraphics();
            myRectangle.Show(gr);
        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            switch (e.KeyCode)//分析按键消息
            {
                //向上
              
                case Keys.Left:
                    if (x >= 5)
                    {
                        x -= 5;
                        pictureBox1.Refresh();
                        myRectangle = new Rectangle(x, y, 80, 30);
                        myRectangle.Show(gr);
                        gr.Dispose();
                        //               drawimage();
                    }
                    break;
                case Keys.Right:
                    if (x <= 315)
                        x += 5;
                    pictureBox1.Refresh();
                    myRectangle = new Rectangle(x, y, 80, 30);
                    myRectangle.Show(gr);
                    gr.Dispose();
                    //           drawimage();
                    break;
            }

        }

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            myRectangle = new Rectangle(x, y, 80, 30);
            gr = pictureBox1.CreateGraphics();
            myRectangle.Show(gr);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;

namespace WindowsFormsApp2
{
    public class Rectangle
    {
        public int x;//坐标
        public int y;
        public int width;//
        public int height;
        public int direction = 0; //方向，0表示停止，1表示向上走，2下，3左，4右
        public System.Timers.Timer timer;//球的timer
        //构造函数
        public Rectangle(int x, int y, int width, int height)
        {
            this.x = x;
            this.y = y;
            this.width = width;
            this.height = height;
            timer = new System.Timers.Timer();
            timer.Interval = 30;
            timer.AutoReset = true;
        }
        public Rectangle() { }
        //将自己画到gr上
        public void Show(Graphics gr)
        {
            Rectangle rt = new Rectangle(x, y, width, height);
            Pen mypen = new Pen(Color.Red, 3);
            gr.DrawRectangle(mypen, x, y, width, height);

        }

    }

}

 Form1_Load中的代码无效，写在pictureBox1_Paint事件里的代码也没有会出图像，Keys.Right和Keys.Left键的代码可以显示图像，我看有的源码是把绘图放在 Form1_Load中，我尝试却不行。