How to add an event to a class painted shape?

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C#

I am not a professional coder. This code is working fine as it is now.
----------
But I want to add an event to this class, that will look similar to a clasic button event, like this:
private void BasicButon_Click(object sender, EventArgs e) { ... }
and fire it up from Form1.
I have no idea how to implement it.
Please modify my code and inject in it this event functionality, then post it as an answer. Thank you.

What I have tried:

//custom class:
    class BasicButon
    {

        int size = 2;
        public int grf = 1;

        public void Draw(int x, int y,  PaintEventArgs e)
        {
            Point[] triunghi1 = { new Point(x + 12 * size, y + 3 * size), new Point(x + 12 * size, y - 3 * size), new Point(x + 17 * size, y) };

            switch (grf)
            {
                case 1:
                    e.Graphics.FillPolygon(new SolidBrush(Color.Red), triunghi1);//red
                    break;
                case 2:
                    e.Graphics.FillPolygon(new SolidBrush(Color.Blue), triunghi1);//blue
                    break;
            }
        }

    }


//and in Form1:
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            bb.grf = 1;
        }

        BasicButon bb = new BasicButon();

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            bb.Draw(20, 20, e);
        }

    }