C#画箭头程序，不知咋把图保存起来！
代码是酱紫！
是直接画在窗体上的
实现了鼠标Move过程中线一直存在！
但是！Clear命令导致之前画的所有线都没了！
我的想法是。。。能不能再MouseDown的时候，把之前画的存起来，画完再加载？？求教啊~我是菜鸟！想用最简单的方法实现先。。。

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 PAINTER
{
    public partial class Form1 : Form
    {
        private Image MyImg;
        int startX, startY;
        Graphics g;
        bool mouseDown = false;
       
         
        public Form1()
        {
            InitializeComponent();
            
        }

        private void radioButton1_CheckedChanged(object sender, EventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.MouseDown += new MouseEventHandler(Form1_MouseDown);
            this.MouseUp += new MouseEventHandler(Form1_MouseUp);
            this.MouseMove += new MouseEventHandler(Form1_MouseMove);
        }
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            mouseDown = true;
            startX = e.X;
            startY = e.Y;
            
        }
        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            mouseDown = false;
            g = this.CreateGraphics();
            
            Pen p = new Pen(Color.Cyan,3);
            System.Drawing.Drawing2D.AdjustableArrowCap lineArrow =
                new System.Drawing.Drawing2D.AdjustableArrowCap(4, 4, true);
            p.CustomEndCap = lineArrow; 
 
            g.DrawLine(p, startX, startY, e.X, e.Y);
        }
        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (mouseDown)
            {
                g = this.CreateGraphics();
                Form1_Paint(this, new PaintEventArgs(this.CreateGraphics(), this.ClientRectangle));
                g.DrawLine(new Pen(Color.Cyan, 1), startX, startY, e.X, e.Y);
            }

        }
        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = this.CreateGraphics();
            g.Clear(Color.White);
            
        }

    }
}

[解决办法]
画在内存bitmap中，Paint事件绘制在窗体上。

g.Clear(Color.White);
这样窗体被覆盖引发Paint，当然就没有了。
[解决办法]
先在Bitmap中画好，然后再绘在窗体上