C#Graphics画图

 public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Graphics g = this.CreateGraphics();//创建GDI对像

            //创建画笔(颜色)
            Pen npen = new Pen(Brushes.Red);

            //创建两个点
            Point n1 = new Point(20, 20);
            Point n2 = new Point(255, 255);

            g.DrawLine(npen, n1, n2);

        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = this.CreateGraphics();//创建GDI对像

            //创建画笔(颜色)
            Pen npen = new Pen(Brushes.Red);

            //创建两个点
            Point n1 = new Point(20, 20);
            Point n2 = new Point(255, 255);

            g.DrawLine(npen, n1, n2);

        }

        private void button2_Click(object sender, EventArgs e)
        {
            Graphics ng = this.CreateGraphics();

            //创建画笔
            Pen npen = new Pen(Brushes.Red);

            Size sz=new System.Drawing.Size(100,100);
            Rectangle res = new Rectangle(new Point(50, 50), sz);

            ng.DrawRectangle(npen, res);
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Graphics g = this.CreateGraphics();

            Pen npen = new Pen(Brushes.Blue);

            Size sz = new System.Drawing.Size(180, 180);

            Rectangle rec = new Rectangle(new Point(150, 150), sz);

            g.DrawPie(npen, rec, -50, -50);
        }

        private void button4_Click(object sender, EventArgs e)
        {
            Graphics g = this.CreateGraphics();

            Pen npen = new Pen(Brushes.Blue);

            g.DrawString("我是中国人", new Font("宋体", 20, FontStyle.Bold), Brushes.Blue, new PointF(29, 29));
        }