winform 制作圆形图片框

public partial class CirclePictureBox : PictureBox
    {
        public CirclePictureBox()
        {
            Circle = true;
            InitializeComponent();
        }        

        protected override void OnPaint(PaintEventArgs pe)
        {            
            base.OnPaint(pe);            
        }

        //圆形大小随控件大小变化
        protected override void SetBoundsCore(int x, int y, int width, int height, BoundsSpecified specified)
        {
            if (width > 0 && height > 0)
            {
                CircleSize = new Size(width, height);
            }
            base.SetBoundsCore(x, y, width, height, specified);
        }

        bool _circle;
        [Description(" 获取或设置按钮椭圆效果。"), DefaultValue(true)]
        public bool Circle
        {
            get
            {
                return _circle;
            }

            set
            {
                if (value)
                {
                    GraphicsPath gp = new GraphicsPath();
                    gp.AddEllipse(0, 0, _circleSize.Width, _circleSize.Height);//圆形                       
                    this.Region = new Region(gp);
                    this.BorderStyle = BorderStyle.None;
                    this.Invalidate();
                }
                _circle = value;
            }
        }

        Size _circleSize=new Size(50,50);
        [Description(" 圆形的大小")]
        Size CircleSize
        {
            get
            {
                return _circleSize;
            }
            set
            {
                _circleSize = value;
                Circle = true;
            }
        }
    }