c#已知一个圆的圆心的坐标和半径，怎样画一个圆

Question

如图

Answer 1

在onpaint事件中            Point center = new Point(100, 100);
            int r = 20;
            Rectangle rect = new Rectangle(center.X-r,center.Y-r,center.X+r,center.Y+r);
            e.Graphics.DrawEllipse(Pens.Red, rect);

Answer 2

http://www.cnblogs.com/heluo/articles/2390804.html

Answer 3

在控件的OnPaint事件中，用e.Graphic绘制就可以了

Answer 4

以下代码实现的是以两条线交叉的点为圆心画圆，但是不对啊，麻烦给看一下，是哪错了private void button2_Click(object sender, EventArgs e)
        {
            //this.pictureBox1.Visible = false;
            int x1 = this.pictureBox2.Width;
            int y1 = this.pictureBox2.Height;
            int x2=this.pictureBox2.Width/2;
            int y2=this.pictureBox2.Height/2;            Point p1 = new Point(x2, 0);
            Point p2 = new Point(x2, y1);
            Point p3 = new Point(0, y2);
            Point p4 = new Point(y1, y2);            Graphics g = this.pictureBox2.CreateGraphics();
            Pen p = new Pen(Color.Red);
            g.DrawLine(p, p1, p2);
            g.DrawLine(p, p3, p4);            Point p5 = new Point(x2,y2);
            int r = 20;
            Rectangle rect = new Rectangle(p5.X - r, p5.Y - r, p5.X + r, p5.Y + r);
            g.DrawEllipse(Pens.Red, rect);
                     }