ElipseControl.cs

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace R804MoverFigura
{
    public partial class ElipseControl : UserControl
    {
        private GraphicsPath path = null;

        public ElipseControl()
        {
            InitializeComponent();
        }

        private void ActualizarPath()
        {
            path = new GraphicsPath();
            path.AddEllipse(this.ClientRectangle);
            this.Region = new Region(path);
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);

            if (path != null)
            {
                e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
                e.Graphics.FillPath(new SolidBrush(this.BackColor), path);
                e.Graphics.DrawPath(new Pen(this.ForeColor, 4), path);
            }
        }

        protected override void OnResize(EventArgs e)
        {
            base.OnResize(e);
            ActualizarPath();
            Invalidate();
        }
    }
}