public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
protected override void OnPaint(PaintEventArgs e)
{
Graphics g=e.Graphics;
using (Pen blackPen=new Pen(Color.Black,1))
{
for(int y=0;y<ClientRectangle.Height;y+=ClientRectangle.Height/10)
{
g.DrawLine(blackPen,new Point(0,0),new Point(ClientRectangle.Width,y));

}

}

}
}

using (Pen blackPen=new Pen(Color.Black,1))
这是什么意思。怎么下面还有括号？？

还有为什么 程序启动会自动执行

protected override void OnPaint(PaintEventArgs e) 这个方法

自己顶

using (Pen blackPen=new Pen(Color.Black,1))

其实就相当于在这段代码前加上
using System;
然后using (Pen blackPen=new Pen(Color.Black,1))
就可以变为Pen blackPen=new Pen(Color.Black,1)

override重载了方法onpaint．

如果不想让它自动执行，可这样写：
private void button1_Click(object sender, System.EventArgs e)
{
Graphics g=this.CreateGraphics();
using (Pen blackPen=new Pen(Color.Black,1))
{
for(int y=0;y<ClientRectangle.Height;y+=ClientRectangle.Height/10)
{
g.DrawLine(blackPen,new Point(0,0),new Point(ClientRectangle.Width,y));
}
}
}