namespace WindowsFormsApplication1

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }



        Point P1 = new Point();

        Point P2 = new Point();

        bool isMouseDown = false;



        private void Form1_MouseUp(object sender, MouseEventArgs e)

        {

            isMouseDown = false;

            DrawTY(this.CreateGraphics(), P1.X, P1.Y, P2.X - P1.X, P2.Y - P1.Y);

        }



        private void Form1_Load(object sender, EventArgs e)

        {

            

        }



        private void Form1_Paint(object sender, PaintEventArgs e)

        {



            Graphics g = e.Graphics;

         

        }



        private void DrawTY(Graphics g, int a,int b,int c,int d )

        {

            GraphicsPath roundedRect = new GraphicsPath();

            roundedRect.AddArc(a, b, c, d, 200, 360);

       



            //从路径中创建区域

            Region pathRegion = new Region(roundedRect);

           // g.FillRegion(new SolidBrush(Color.Blue), pathRegion);

            g.DrawPath(Pens.Blue, roundedRect);



        }



        private void Form1_MouseDown(object sender, MouseEventArgs e)

        {

            if (isMouseDown == false)

            {

                isMouseDown = true;



                P1.X = e.X;