画图重绘疑问

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 面向对象小项目之飞机小游戏
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
         

        }
        Plane pla = new Plane();//飞机对象
        Bullet bul = new Bullet();//子弹对象
        private void Form1_Load(object sender, EventArgs e)
        {
            pla.StartInit();
            bul.StatInit();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            pla.Move(panel1);
            bul.Move(panel1);
            this.Invalidate();
   
        }
     
        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            pla.Draw(panel1, panel1.CreateGraphics());
            bul.Draw(panel1, panel1.CreateGraphics());
            bul.IsHit(pla, panel1);
            
            
        }
        /// <summary>
        /// 鼠标点击
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void panel1_MouseClick(object sender, MouseEventArgs e)
        {
            bul.SatrtFire(e, panel1);
        }


    }
}

//子弹类的代码
namespace 面向对象小项目之飞机小游戏
{
    class Bullet:GameObject
    {
        /// <summary>
        /// 绘制子弹
        /// </summary>
        /// <param name="p"></param> 
 
        /// <param name="g"></param>
        public override void Draw(Panel p, Graphics g)
        {
          
            
            g.FillEllipse(Brushes.Black ,this.X1, this.Y1, this.Size, this.Size);
        }
        /// <summary>
        /// 子弹移动
        /// </summary>
        /// <param name="p"></param>
        public override void Move(System.Windows.Forms.Panel p)
        {
            //if(this.Y1 < 0)
            //{

            //}
            this.Y1 -= this.Speed;
        }
        /// <summary>
        /// 初始化
        /// </summary>
        public void StatInit()
        {
            this.Speed = 5;
            this.X1 = 0;
            this.Y1 = 500;
            this.Size = 40;

        }
        /// <summary>
        /// 开始攻击
        /// </summary>
        public void SatrtFire(MouseEventArgs e,Panel p)
        {
            this.Y1 = p.Height;
            this.X1 = e.Location.X;

        }
        /// <summary>
        /// 是否打中飞机
        /// </summary>
        /// <param name="p"></param>
        /// <param name="p1"></param>
        public void IsHit(Plane p,Panel p1)
        {
            if (this.X1 == p.X1 || this.Y1 == p.Y1)
            {
                if (p.HitTimes < 3) 
 
                {
                    p.Glimmer(p1);
                }
                else
                {
                    MessageBox.Show("哈哈！你打中飞机了！");
                }
            }
        }
        
    }
}

我的飞机图片可以正常重绘 可是子弹却还残留上次的 造成图片中的这样 修改多次无果
[解决办法]
private void Form1_Paint(object sender, PaintEventArgs e)
{
panel1.Refresh(); //加一句
pla.Draw(panel1, panel1.CreateGraphics());
bul.Draw(panel1, panel1.CreateGraphics());
bul.IsHit(pla, panel1);
}
[解决办法]
既然在panel1中重绘 你不应该使用Form1的paint事件，你应该使用panel1的重绘事件

private void panel1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
    Graphics g = e.Graphics;
    bul.Draw(g);
}

public override void Draw(Graphics g)        
{                        
     g.FillEllipse(Brushes.Black ,this.X1, this.Y1, this.Size, this.Size);         
}
public override void Move(System.Windows.Forms.Panel p)         
{                         
      this.Y1 -= this.Speed;  
      p.Refresh();//自己控制刷新时机       
} 

以上写法应该能保证你在panel上重绘
[解决办法]
嗯，放到panel的OnPaint中