C#绘制椭圆的方法

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace WindowsApplication2
{
  public partial class Form4 : Form
  {
    public Form4()
    {
      InitializeComponent();
    }
    bool drawElipse = false;
    private void button1_Click(object sender, EventArgs e)
    {
      this.drawElipse = !this.drawElipse;
      using (Graphics g = this.CreateGraphics())
      {
        if (this.drawElipse)
        {
          g.FillEllipse(Brushes.DarkBlue, this.ClientRectangle);
        }
        else
        {
          g.FillEllipse(SystemBrushes.Control, this.ClientRectangle);
        }
      }
    }
    private void Form4_Load(object sender, EventArgs e)
    {
    }
  }
}