线性梯度画刷

using (Graphics graphics = this.CreateGraphics())
            {// graphics.Clear(Color.White);
                Pen pen = new Pen(Color.Red, 2);
                //SolidBrush brush = new SolidBrush(Color.Black);
                //定义一个渐变线偏转角度为30度的渐变画刷，大小40*20
                LinearGradientBrush lgb = new LinearGradientBrush(
                    new Rectangle(0, 0, 40, 20),
                    Color.Green,
                    Color.Blue, 45.0f);
                //使用偏转角度为30度的渐变画刷填充区域
                graphics.FillRectangle(lgb, new Rectangle(150, 20, 120, 120));
                graphics.DrawRectangle(pen, new Rectangle(150, 20, 120, 120));
            }