protected override void OnPaint(PaintEventArgs e)
{
base.Onpaint(e);
//定义画布
Graphics g=e.Graphics;
//定义一个矩形(当前窗体)
Rectangle rec=new Rectangle (0,0,this.Width,this.Height);
//定义一个带渐变色的画刷,LinearGradientMode为渐变色的填充方式
LinearGradientBrush brush=new LinearGradientBrush(rec,Color.FromArgb(220,100,200),Color.FromArgb(90,120,125),LinearGradientMode.Vertical);
//填充矩形
g.FillRectangle(brush,rec);
}