private Point p1, p2;//定義兩個(gè)點(diǎn)（啟點(diǎn)，終點(diǎn)）
private static bool drawing=false;//設(shè)置一個(gè)啟動(dòng)標(biāo)志
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        
       p1 = new Point(e.X, e.Y);
       p2 = new Point(e.X, e.Y);
        drawing = true;
      
    }
 
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
      drawing = false;
    }
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
 
    {
     
      Graphics g = pictureBox1.CreateGraphics();
      if(e.Button ==MouseButtons.Left)
      {
        if (drawing)
        {
          //drawing = true;
          Point currentPoint = new Point(e.X, e.Y);
          g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//消除鋸齒
          g.DrawLine(new Pen(Color.Blue, 2), p2,currentPoint);
          
          p2.X = currentPoint.X;
          p2.Y = currentPoint.Y;
        }
 
      }
      
    }
//清屏操作
private void button1_Click(object sender, EventArgs e)
{
 Graphics g = pictureBox1.CreateGraphics();
 g.Clear(Color.White);
}