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(, );

            Point n2 = new Point(, );

            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(, );

            Point n2 = new Point(, );

            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(,);

            Rectangle res = new Rectangle(new Point(, ), 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(, );

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

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

        }

        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", , FontStyle.Bold), Brushes.Blue, new PointF(, ));

        }