自动绘制相关图形及实现渐变颜色

因为用到了椭圆及渐变效果，所以需引用以下的命名空间：

using System.Drawing;
using System.Drawing.Drawing2D;

代码实现技术如下：

private void Form1_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
Brush brGradient = new LinearGradientBrush(new Rectangle(0,0,400,400),Color.Black,Color.Red,45,false);
Brush brHatch = new HatchBrush(HatchStyle.HorizontalBrick, Color.Black, Color.Yellow);
Brush brsolid = new SolidBrush(Color.SlateBlue);

g.FillRectangle(brGradient,10,10,200,180); //画正方形
g.FillEllipse(brHatch,150,200,150,190); //椭圆
g.FillPie(brsolid,80,0,300,300,285,75); //扇形
}

实现效果图：