using System;

using System.Drawing;

using System.Windows.Forms;

using System.Drawing.Drawing2D;

​

namespace WindowsFormsApp13

{

    public partial class MyCheckbox : PictureBox

    {

        public bool Checked {

            get => isChecked;

            // use a custom setter, because the controls appearence changes with this variable

            set {

                isChecked = value;

                // always use Invalidate() to tell the message loop to redraw (aka call OnPaint())

                Invalidate();

            }

        }

​

        private bool isChecked;

        private bool hovered;

​

        public MyCheckbox()

        {

            InitializeComponent();

            Checked = false;

        }

​

        protected override void OnPaint(PaintEventArgs pe)

        {

            base.OnPaint(pe);

            Graphics g = pe.Graphics;

​

            g.SmoothingMode = SmoothingMode.AntiAlias;

            g.Clear(Color.White);

​

            float width = g.VisibleClipBounds.Width;

            float height = g.VisibleClipBounds.Height;

​

            if (Checked)

            {

                Pen p = new Pen(Color.Green, 3);

                g.DrawLines(p, new PointF[] {

                    new PointF(0, height/2),

                    new PointF(width/2, height),

                    new PointF(width, 0)

                });

            }

            else

            {

                Pen p = new Pen(Color.Red, 3);

                g.DrawLine(p, new PointF(0, 0), new PointF(width, height));

                g.DrawLine(p, 0, height, width, 0);

            }

​

            if (hovered)

            {

                Pen p = new Pen(Color.Blue, 3);

                g.DrawRectangle(p, 0, 0, width, height);

            }

​

        }

​

        protected override void OnClick(EventArgs e)

        {

            base.OnClick(e);

            Checked = !Checked;

            Invalidate();

        }

​

        protected override void OnMouseEnter(EventArgs e)

        {

            base.OnMouseEnter(e);

            hovered = true;

            Invalidate();

        }

​

        protected override void OnMouseLeave(EventArgs e)

        {

            base.OnMouseLeave(e);

            hovered = false;

            Invalidate();

​

        }

​

    }

}

​